Research Programme
Engineering Review and Development of Safe Working Practices in Electrified Areas - Report No. 2
Balfour Beatty
Issue: 1.0 Date: 1st December 2006
Project Report
T345 - Review and Development of Safe Working Practices in Electrified Areas – Report No. 2
Prepared for Rail Safety and Standards Board
Balfour Beatty Rail Projects Limited Midland House Nelson Street Derby DE1 2SA WWW.bbrail.com
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EXECUTIVE SUMMARY The Rail Safety and Standards Board's (RSSB's) Research Programme is responsible for the development and delivery of much of the railway industry’s safety-related research and development. RSSB has awarded a contract to Balfour Beatty Rail Projects under this programme for the Review and Development of Safe Working Practices in Electrified Areas. The project aims to review the basis on which practices for isolation and earthing during construction, renewals, commissioning, and maintenance have evolved; and make recommendations for revised standards that will lead to greater safety for workers as well as more effective maintenance possessions. It also looks at issues related to working on functioning electrification systems, such as touch voltages and live line indication. The project is delivered in the form of two separate reports. This report (Report No. 2) addresses the issues of:: how isolation and earthing practices have evolved incidents where human contact with a live conductor have occurred, including human factor analysis tasks undertaken in an electrified railway and the risks associated with them; and training in respect of working on electrical equipment. It also discusses some developments of processes, standards, and equipment, which can lead to enhanced safety and efficiency. Section 3 of this report highlights the standards applicable to the scope of the study and against which the research was conducted. It also lists other pertinent legislation and documents applicable to rail electrification systems including: Railway Safety Principles and Guidance Part 2, Section C Guidance on Electric Traction Systems BS EN 50122-1 1998 Railway Applications – Fixed Installations, Part 1 – Protective Provisions Relating to Electrical Safety and Earthing Network Rail Safety Information Bulletin No IMM/GE/001; August 2004 Traction Return Circuit Continuity Bonds BR 12034/16 Railway Electrification 25kV A.C. Design on B.R. Section 4 of the report sets down the history of the isolation and earthing process and details how it has evolved from pre-World War II to the present day. The review has concluded that the isolation process presented in RT/E/S/29987 is a well proven, methodical way to achieve safe working on or adjacent to 25kV overhead line equipment (OLE). The continuation of the 29987 User Group is seen as key to continuous improvement in the promotion of safe working practices in electrified areas. The review has identified the problem of over issue of overhead line permits on some major work sites due to bad practice and misinterpretation of the rules. It recommends that enhanced communication of rulebook requirements is undertaken in this area. The continued use of long earths in the absence of designated earthing points (DEPs) is a cause for concern and we recommend that a national database of DEPs be progressed in Phase 2 of this project. Knowing and understanding where DEPs are not available will allow action plans to be formulated to mitigate this risk in the future.
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The review has identified the hazards that exist from 25kV OLE. It is felt that benefit could be gained from producing a publication highlighting these hazards to raise awareness/understanding to Controller of Site Safety (COSSs) and Personal Track Safety (PTS) holders. The level and content of electrification training on both PTS and COSS courses is a cause for concern and we recommend that Phase 2 of this project reviews both PTS and COSS course content and with the collaboration of Network Rail and Sentinel produces new slides, training plans, and assessment tools. The project recognises the good work already undertaken on the changes to Standards and processes for AC overhead line nominated persons (NP) and authorised persons (AP). The review has highlighted non-compliance issues with Module 6 of RT/E/S/29987 in regard to isolation planning, it is however, recognized that this non-compliance is being addressed by the 29987 User Group. The importance of identifying all recipients of overhead line permits in pre-planning is covered in clause 4.16 of this report. The over issue of permits to COSSs and machine controllers whose work activity does not require an isolation is another area of concern and needs to be addressed in both training and cascade briefing. Review of electrical clearances to earth has identified differences in the various publications covering this issue and in particular in the Railway Safety Principles and Guidance Part 2 Section C. We recommend a detailed review of electrical clearances given in these documents by the various stakeholders, and that a uniform approach be agreed. The human factors element of the study set out to achieve the following objectives: Review existing literature to identify any previous work on electrified areas, to avoid duplication of effort Review a sample of railway incidents involving electrified equipment to determine why the people involved behaved the way that they did. Predict the types of human error that could feasibly occur considering the tasks that personnel are required to perform in and around electrified areas. Previous research has provided a great deal of practical information on why people behave (intentionally or unintentionally) in a way that goes against safety procedures, including recommendations for the reduction of such behaviours in the future. There is also best practice guidance available on teamwork within the rail industry, which is written in such a way as to make translation into recommendations relatively simple. This guidance can be used to identify ways of reducing the likelihood of teamwork failures in future. Research into communications errors during railway maintenance suggests that the primary cause of such errors is the design and usability of communications procedures. Research into distance judgement suggests that even experienced crane operators find it very difficult to judge accurately the clearance from overhead lines. In cases where raising part of a vehicle could expose the occupants to the risk of electrocution, the use of distance markers should be considered.
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As part of the human factors input to this project, a predictive error analysis was conducted using the task-based risk assessments developed by OLE and DC electrification specialists from Balfour Beatty Rail. The object of this exercise was to predict the types of human error that could occur whilst working in AC or DC electrified areas. The predictive analysis of human error conducted to supplement the risk assessment of tasks conducted in electrified areas suggested that the predominant types of error that would be encountered would be perception, action and memory errors. Most tasks do not provide the opportunity for decision-making errors, although these were also predicted. Expert opinion suggested that decision-making errors would be more likely in planning and management tasks than in manual tasks. In the majority of cases, applying the rules laid down in either RT/E/S/29987 or GO/RT3091 will result in specific risk assessment of the task and a safe system of work to be developed thereby lowering the risk to a tolerable level. The identification of risks in third rail areas was initiated following the introduction of Issue 3 of GO/RT3091 but this work stalled upon its withdrawal. It is recommended that this work is reinitiated. A number of recent innovations in the process of being developed or at a point where a development would enhance safety or efficiency are presented at Section 8. Further work should be undertaken in Phase 2 of this project to introduce developments that will offer improvement. An area of concern in the introduction of innovation or development is the apparent lack of change management culture within the industry, which delays introduction of good ideas and does not make them visible.
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Contents EXECUTIVE SUMMARY............................................................................................................................ 1 1
INTRODUCTION ................................................................................................................................ 6
2
BACKGROUND ................................................................................................................................... 7
3
REVIEW OF PERTINENT DOCUMENTATION ........................................................................... 8
3.1 3.2 3.3 3.4 4
Railway Group Standards ................................................................................................ 8 Network Rail Company Standards .................................................................................. 9 Other documentation considered ..................................................................................... 9 Legislation ....................................................................................................................... 9
EVOLUTION OF 25 KV OLE ISOLATION AND EARTHING PROCESSES .......................... 11
4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 4.22
Introduction.................................................................................................................... 11 The Isolation & Earthing Process .................................................................................. 12 Isolation Process Flowchart ........................................................................................... 14 Isolation and Earthing Process – Control Measures ...................................................... 15 Issue of Overhead Line Permits..................................................................................... 16 Hazard from 25kV overhead line equipment................................................................. 17 Typical residual 25kV hazards ...................................................................................... 17 Planning and 25kV Residual Hazards............................................................................ 21 Hazard and Risk-Based Briefing ................................................................................... 21 PTS Electrification Training.......................................................................................... 22 COSS Electrification Training....................................................................................... 22 Nominated and Authorised Persons Competence.......................................................... 22 Compliance with Isolation Procedures .......................................................................... 22 Isolation Planning .......................................................................................................... 23 Alternative Methods of Issuing Overhead Line Permits................................................ 23 Identification of Overhead Line Permit Recipients ....................................................... 24 Over Issue of Overhead Line Permits............................................................................ 24 The Origin and Purpose of the ‘9 foot rule’ (sic)........................................................... 25 25kv Electrical Clearances to Members of the Public on Station Platforms ................. 26 Clearances to Members of the Workforce and Public in EN 50122-1........................... 28 Electrical Clearances to Earth........................................................................................ 29 25kV electrical clearances to earth summarised:........................................................... 30
5
CONSIDERATION OF DC THIRD RAIL ISOLATION AND EARTHING PROCESSES ...... 31
6
HUMAN FACTOR ANALYSIS........................................................................................................ 32
6.1 6.2 6.3 6.4 6.5 6.6 6.7 7
TASK IDENTIFICATION AND RISK ANALYSIS ....................................................................... 67
7.1 7.2 7.3 8
Introduction.................................................................................................................... 32 Literature Review .......................................................................................................... 32 Review of Historical Incident Data ............................................................................... 36 Results of Review of Historical Incident Data .............................................................. 39 Conclusions.................................................................................................................... 49 Recommendations.......................................................................................................... 53 Predictive Error Analysis............................................................................................... 56 Methodology.................................................................................................................. 67 Example of Task Identification and Risk Assessment Process...................................... 69 Summary........................................................................................................................ 70
DEVELOPMENTS............................................................................................................................. 73
8.1
Report No. 2
Introduction.................................................................................................................... 73
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8.2
Specific Developments .................................................................................................. 73
9
CONCLUSIONS ................................................................................................................................. 78
10
RECOMMENDATIONS.................................................................................................................... 81
10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8 10.9 10.10 10.11 10.12 10.13 10.14 10.15 10.16 10.17 10.18 10.19 11
Introduction.................................................................................................................... 81 Recommendation 1 – Communications ......................................................................... 81 Recommendation 2 – Vertical Slice Audits................................................................... 81 Recommendation 3 – National Database of DEP Locations ......................................... 81 Recommendation 4 – PTS and COSS Training............................................................. 81 Recommendation 5 – Electrical Clearances to Earth..................................................... 81 Recommendation 6 - Safety Observation Schemes ....................................................... 81 Recommendation 7 - Greater Emphasis on Supervisory Checks .................................. 82 Recommendation 8 - Introduce Safety Communications Training ............................... 82 Recommendation 9 - Checking the Planning Process ............................................... 82 Recommendation 10 - Further Analysis.................................................................... 82 Recommendation 11 - Incident Reporting................................................................. 82 Recommendation 12 – RIMINI Approach ................................................................ 82 Recommendation 13 – Tasks on the DC Third Rail.................................................. 82 Recommendation 14 – Development - Live Line Indicators..................................... 83 Recommendation 15 – Development - Live Line Testers ......................................... 83 Recommendation 16 – Development - Live Line Data Loggers............................... 83 Recommendation 17 – Development - Conductor Rail Gauging.............................. 83 Recommendation 18 – Mandated use of PPE in DC Conductor Rail Areas ............. 83
REFERENCES ................................................................................................................................... 84
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1 Introduction The Rail Safety and Standards Board's (RSSB's) Research Programme is responsible for the development and delivery of the railway industry’s safety-related research and development. RSSB have awarded a contract to Balfour Beatty Rail Projects under this programme for the Review and Development of Safe Working Practices in Electrified Areas. The project aims to review the basis on which practices for isolation and earthing during construction, renewals, commissioning and maintenance have evolved, and to make recommendations for revised standards that will lead to greater safety for workers as well as more effective maintenance possessions. It also looks at issues related to working on functioning electrification systems, such as touch voltages and live line indication. The project is delivered in the form of two separate reports. This report (Report No. 2) addresses the issues of: how isolation and earthing practices have evolved; incidents where human contact with a live conductor have occurred, including human factors analysis; tasks undertaken in an electrified railway and the risks associated with them; and training in respect of working on electrical equipment. It also discusses some developments with processes, standards and equipment, which can lead to enhanced safety and, in addition, efficiency without compromise to safety. Report No. 1 considers some fundamental electrical issues that impact on safety. In particular, it focuses on the voltages that appear on the running rails, and on connected non-live conductive structures, under a variety of conditions. It also considers the influence of the protection system in determining the length of time for which elevated rail voltages may persist during a short circuit. The study has focussed on 25 kV AC systems because potentials that are high enough to present a safety risk are much more likely to occur, when compared with DC third rail systems.
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2 Background The electrification system and the associated operating procedures have been designed for safe operation. Many changes have occurred over recent years, which include: Infrastructure changes, including new auto transformer systems, switchgear, protection devices, etc New rolling stock, with greater power demand Increased traffic density, requiring higher fault levels Operational changes that have affected the management of both infrastructure and trains Disaggregation of the rail industry into many smaller service providers, many with little history of railway working and in particular electrification systems Although it is generally recognised that change is effectively managed by the Safety Case requirements and that standards and procedures are amended to reflect the change, concern remains within the industry regarding both workforce and passenger safety. The risk of electrocution from contact with an energised conductor remains high, and any mitigation of this risk is desirable. The move to privatisation resulted in a massive loss of skill and expertise at all levels in the rail industry. In many cases, the people who were lost were the people who set the standards that form the basis of what is in place today. When these people moved on they took with them the corporate memory which formed the decision making criteria of what was done and why. The corporate memory issue is further compounded by the disaggregation brought about by privatisation with no one body holding all the information. The disaggregation of the rail industry has resulted in a need for many independent organisations providing discrete services to interface with each other. This demands much better controls and communications to be applied to ensure safety for both the workforce and the travelling public. The desire to achieve increased passenger growth has seen an increase in traffic density, which in turn limits the availability for access to the infrastructure for maintenance and renewal purposes. Improvements in efficiency in taking isolations and applying earths is seen as key in ensuring the future condition of the rail network as a whole, although this must be achieved without compromise to safety in taking the isolation or provision of a safe system of work.
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3 Review of Pertinent Documentation There is a plethora of documents which cover the subject matter contained within this research ranging from railway safety principles and guidance produced by the HSE, other legislative documents, Railway Group Standards, Network Rail Company Standards and European Standards. The standards listed below were used as the basis for this research.
3.1
Railway Group Standards
Document no Date/ Issue GL/RT1252
Apr-00/1
GL/RT1254
Apr-00/1
GM/RT1040
Aug-96/1
GI/RT7007
Jun-02/1
GI/RT7033
Jun-03/1
GE/RT8024
Oct 2000/1
GE/RT8025
Oct 2001/1
GO/RT3091
Apr 1998/2
GO/RT3093
Dec 1999/2
GO/RT3260
Aug 1998/2
GO/RT3279
Dec 1999/5
GO/RC3560
Aug 1998/1
Title
Synopsis
Production & Management of Electrification Isolation Documents Electrified Lines Traction Bonding Safe Working on or Near Electrical Equipment
Defines the requirements for the production & management of isolation documents for all electrified lines Mandates the requirements for electrified lines traction bonding The requirements for providing a safe system of work Defines the requirements for low voltage Low Voltage Electrical installations on Network Rail controlled Installations infrastructure This document mandates the arrangements for the management & specification of lineside operational Lineside Operational Safety Signs safety signs in order to provide consistency of form and presentation throughout the network. Defines the requirements for the production of safe systems of work to prevent injury for electrical Persons Working on or near to AC causes to persons working on or near to Network Electrified Lines Rails AC Overhead line equipment that danger may arise. Mandates the design requirements for the avoidance Electrical Protective Provisions of direct contact between persons and live parts of for Electrified Lines electrification equipment and of electrical equipment on trains These instructions set out the actions to be taken to avoid danger from DC electrified lines or the DC Electrified Lines Instructions process to be followed to determine the actions to be taken to avoid such danger. The minimum requirements for planning The Planning Requirements for engineering work to ensure the risks to operational Operational Safety of Engineering safety are effectively controlled to be as low as Work reasonably practicable. Clarifies the application of the Railways (Safety Critical Work) Regulations to Network Rail Competence Management for controlled infrastructure, and defines requirements Safety Critical Work for systems for managing the competence and fitness of persons required to undertake such work. Sets out the minimum requirements for high High Visibility Clothing visibility clothing The recommended components of a competence Code of Practice - Competence assessment system to assist compliance with Assessment GO/RT3260 Competence Management for Safety Critical Work
Table 1 Railway Group Standards
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3.2
Network Rail Company Standards
Document No. Date/Issue Title NR./SP/ELP/27154 Procedure for the use and care of BR Type Testers Procedure for use of Permaquip Scissors type platform machine and High NR./SP/ELP/27150 Capacity Trolleys as used for OHL Maintenance Maintenance of Mark IIIB Overhead line equipment (formerly NR./SP/ELP/27214 EHQ/ST/O/003) Procedure for the Issue, Storage, Routine Inspection and Testing of NR./SP/ELP/27171 Rubber Gloves Specification for the provision of isolation, earthing and indication NR./SP/ELP/27203 facilities where local isolations are permitted on AC Electrified Lines Specification for the preparation of isolation diagrams and instructions EHQ/SP/S/030 for AC Electrified Lines RT/CE/C/033 Historical Competence requirements for safety critical permanent way work NR/GN/ELP/00004 AC Electrified Lines Earthing and Bonding NR/SP/ELP/24009 Competence requirements for Electrical Control Room Operators Index of Railtrack documents relating to Electromechanical plant RT/E/S/20000 Historical engineering activities Instruction for making out, issuing and cancelling HV Permits to work, NR/SP/ELP/21067 sanctions to test and circuit state certificates Competence of persons working on or having access to Electrical Power NR/SP/ELP/21070 supply equipment Appointment, Training & Assessment of Persons Working On or having NR/SP/ELP/24001 access to Electrical Power Supply Equipment for Railway Traction NR/SP/ELP/21085 Design of earthing and bonding systems for 25 kV AC electrified lines NR/SP/ELP/21131 Warning and other signs for AC & DC Electrified Lines Working on or about 25kV AC Electrified Lines (formerly NR/SP/ELP /29987 RT/E/S/29987) RT/LS/P/006 Maintenance and contents of the National Hazard Directory EHQ/SP/S/030 Jan 1992 Specification for the preparation of Isolation Diagrams and Instructions NR/WI/ELP/2708 Dec 2004 Instruction for the Layout of Overhead line equipment Table 2 Network Rail Company Standards
3.3
Other documentation considered Railway Safety Principles and Guidance Part 2 Section C - Guidance on Electric Traction Systems BS EN 50122-1 1998 Railway Applications – Fixed Installations, Part 1 – Protective Provisions Relating to Electrical Safety and Earthing Network Rail Safety Information Bulletin No IMM/GE/001; August 2004 Traction Return Circuit Continuity Bonds BR 12034/16 Railway Electrification 25kV a.c. Design on B.R. (historical document)
3.4
Legislation
This section is not an exhaustive review of pertinent legislation, rather it picks out the headlines as they influence the people and equipment involved in the isolation process. As far as employers and employees conduct themselves relating to particular activities in the isolation process, the Health and Safety at Work etc Act 1974 (HASAW) requires that:
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‘It shall be the duty of every employer to ensure, so far as is reasonably practicable, the health, safety and welfare at work of all his/her employees. It shall be the duty of every employee while at work: To take reasonable care for the health and safety of himself and of other persons who may be affected by his acts or omissions at work; and To co-operate with the employer as far is necessary in order for statutory obligations to be met.’ As far as employers and employees discharge their responsibilities regarding competence within the isolation process, the Railways (Safety Critical Work) Regulations 1994 Approved Code of Practice and Guidance states: ‘The HASAW (Health and Safety at Work etc Act 1974) and MHSWR (Management of Health and Safety at Work Regulations 1999) combine to require all employers to ensure that employees are competent to carry out their tasks without risk to the health and safety of themselves and others. ‘Competence’ means that employees must have the necessary skills, experience, knowledge and personal qualities. Employers must specify essential requirements and ensure, through selection criteria for personnel, and by the provision of necessary information, instruction, training and supervision, that the demands of a task do not exceed the individual’s ability to carry it out without undue risk.’ As far as the system requirements are concerned relating to the isolation activity, the Electricity at Work Regulations (1989) require that (abridged extracts): ‘Suitable means (including, where appropriate, methods of identifying circuits) shall be available for: Cutting off the supply of electrical energy to any electrical equipment The isolation of any electrical equipment Isolation means the disconnection and separation of electrical equipment from every source of electrical energy in such a way that this disconnection and separation is secure Adequate precautions shall be taken to prevent electrical equipment, which has been made dead in order to prevent danger while work is carried out on or near that equipment, from becoming electrically charged during that work if danger may thereby arise’
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4 Evolution of 25 kV OLE Isolation and Earthing Processes 4.1
Introduction
This section of the report is aimed at people who already have a basic knowledge of 25 kV AC isolation procedures and terminology. Experience with main line electrification started just before the Second World War with LNER projects to electrify the GE lines between Liverpool Street and Shenfield, and the MSW or ‘Woodhead Line’ from Manchester. After nationalisation in 1948, British Rail continued to electrify the network, and various documents for individual schemes and regions were produced, until the British Railways Board produced BR 29987 ‘Working Instructions for 25 kV AC Electrified Lines’ in 1967. Electrification staff know this publication as the ‘Green Book’, an informal title that persists to this day. This document has been revised numerous times, and was re-written into modular format by Railtrack as Company Specification RT/E/S/29987 in 1998. The isolation process prescribed in RT/E/S/29987 is a well-proven, methodical way to achieve safe working on or adjacent to 25kV overhead line equipment. Over time, it has proved itself suitable for the task, based on the relatively low number of incidents that have occurred, and general satisfaction with the time taken to issue an overhead line permit. Network Rail continues regular and ongoing review of this document and it remains the electrification document for risk assessment, planning, and delivery of 25kV AC isolations. The actions described are well established and universally applied to effect isolation. However they were developed for British Rail maintenance and renewal activities, rather than the need to issue numerous (25+) overhead line permits on a current major work site. It is this latter, now common, requirement that stretches the suitability of the standard method of issuing overhead line permits. An alternative method of issuing overhead line permits was introduced as an option in RT/E/S/29987 from February 2005. The likelihood of this alternative option being selected can be low if: The high number of overhead line permits required is only revealed on the night when the nominated person actually has to issue them. It is therefore too late to plan and implement an alternative method of issuing permits (which could safely speed up the process). The high number of permits that require issuing may be due to the following bad practice: The issue of overhead line permits to every COSS and Machine Controller regardless of whether their work activity requires it (which takes extra time and undermines the value of the permit) These two issues are detailed further on in the text. While the infrastructure and planned isolation involves manual switching and application of portable earths on-site, the issue of overhead line permits will always take a finite time, but it can be as short as thirty minutes if planned and implemented properly. It is recommended that when changes to the rules occur, enhanced communication to publicise the changes be effected. This could take the form of industry wide alerts to re-iterate the requirement of the Rulebook; poster campaign; cascade briefing to industry through Safety Net or other suitable media.
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It is also recommended that vertical slice audits of the isolation process be undertaken to determine the effectiveness of the Standard and the process. The vertical slice audit should start with GE/RT 8024 compliance including the requirements of RT/E/S/29987. There are various parts of the process, which are not implemented thoroughly or fall into place later than is ideal: Whilst isolation planning occurs as far out as 40 to 26 weeks before implementation, the detailed possession planning and submission of the Isolation Details Form (IDF) to the Electrical Control Room occurs in the week preceding the isolation, compressing the planning process considerably at the end. This is due to the associated possession meetings (sometimes referred to as the ‘PICOP’ meeting) occurring in the week immediately preceding the isolation. A complete list of overhead line permit recipients should be available to the Nominated Person prior to the isolation being implemented, but it is often incomplete or omitted to the disadvantage of the Nominated Person. This is not due to the lack of clarity of the requirement, rather that the company requiring the Overhead line permits has not identified the total list of named COSSs requiring permits. This can be supplied at the final prepossession meeting or at the latest in the final two days before the isolation. Many companies and projects have demonstrated that this requirement can be achieved, but it remains a frustrating and ongoing omission in some parts of the UK network.
4.2
The Isolation & Earthing Process
Please refer to the Isolation Process Flowchart in section 4.3 The method of switching off and isolating the traction supply to overhead line equipment is a standard process using remotely controlled circuit breakers to switch off the traction supply. Where isolation of complete electrical sections is required, the circuit breakers remain open and form the point-of-isolation. Where part-sections are required, structure mounted overhead line isolators are also operated, either manually or at certain locations, remotely. After operation, they form the point of isolation, and the circuit breakers may be re-closed to energise adjacent part sections that are not part of the isolation. In each case a lock or inhibit is applied to prevent unauthorised operation during the period of the isolation. The method of earthing OLE was standardised from the mid 1980s by the introduction of designated earthing points (DEPs) with defined earth application points (EAPs). These enabled short, pole-applied earths to be applied at high level, which in normal use the operator cannot make contact with, regardless of any irregularity with the isolation. It is also by design less susceptible to being removed or damaged by the passage of trains or on-track machines. The long earth that it superseded for general use relies on operator competence to ensure that the earth end is always applied first and removed last and tied back to prevent collision with trains or on track machines. When applied in the correct sequence there is no danger to the operator, but if the earth end is applied last or removed first, the operator will be exposed to whatever voltage is present on the overhead line equipment. There are many permutations of this irregularity, but one such example is the fatal accident at Ranskill (ECML) in 1998.
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Long earths are still in regular use for certain applications, but should be subject to defined methods of use and control (local management instructions or M&EE COP 1001). Long earths may be required because: Historically, the installation of DEPs was not completed The EAP may be broken In each case, a plan of action is required to avoid the continued use of long earths. A database of DEP locations is very useful in checking and monitoring any corrective action required and to support isolation planning or walkouts. We recommend that a national database of DEP locations be progressed in Phase 2 of this study. Some regional information already exists, and it would be beneficial to gather this information and, using best practice, turn it into a national database.
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4.3
Isolation Process Flowchart
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4.4
Isolation and Earthing Process – Control Measures
The isolation process is robust in that several control measures prevent access to energised equipment. The likelihood of an incident increases if any control measures are stripped away. There is always a set pattern of events after the line has been blocked to electric traction, which is: ISOLATE-TEST-EARTH. The following is not intended to describe this process in detail, rather to examine the control measures and consider the hazardous conditions that can arise if they are not applied. ISOLATING involves switching, as described previously, to disconnect the section of overhead line from all sources of supply. This relies on the electrical control room operator following written documentation to remotely, or manually switch circuit breakers and isolators to remove all sources of electrical supply. If there was a switching error (either human error or equipment fault), and apparently de-energised equipment was in fact still energised, the LIVE-LINE TESTER (LLT) applied to the overhead line equipment (OLE) before the EARTHS were applied would indicate that the line was still energised. The same result would occur if the TESTER were applied to energised OLE outside of the isolated area (i.e. wrong side of section insulation or wrong road). This irregularity (a live reading on the LLT) would immediately be communicated back to the electrical control room for investigation and the isolation suspended until a deenergised reading was obtained. If the mandated TESTING control measure were omitted, the energised condition of the OLE would not be identified until the application of the EARTH. There are two possible results when omitting this control measure: Scenario A: Scenario B:
No adverse reaction - the remaining part of the isolation proceeds normally. The instant circuit breaker trips thereby creating the potential for danger to life.
Scenario A will occur if switching has been carried out correctly removing all electrical supply to the OLE sections and the earths are being applied at the correct locations recorded on the Isolation Detail Form (IDF). Whilst no adverse reaction has occurred, stripping the testing control measure away is not compliant with procedure or training, and leaves no defence against a switching or earth-application point error described next. It is fundamentally a bad practice. Scenario B will result if the electrical supply to the OLE at the earth application point has not been disconnected or the earth is being applied to OLE that is not part of the isolation. Testing prevents Scenario B occurring by ensuring that these activities are carried out correctly BEFORE the earth is applied. The circuit breaker tripping would result in the isolation being cancelled or delayed, a subsequent inquiry, and possible disciplinary action. Where, however, short earths are being applied at a DEP location, tools and equipment are subject to electrical stress and not a member of staff (it is not completely risk free but the short circuit occurs at high level away from the individual applying the earth as described in the previous section). Where these incidents do occur this is the most likely conclusion as short earths are in more common use than long earths. There is the greatest potential danger to life within Scenario B if a long earth is used and applied incorrectly. If wrongly applied live end first, the unsecured earth end at ground level would be live at 25kV. This most dangerous situation would only occur if training was ignored, but it is physically possible (see development section for an improvement to this). All NPs and APs are rigorously trained and assessed to apply the earth end first when using long earths. Short earths applied at DEPs have removed this hazard to the operator, a key reason why they were introduced. It should be emphasised that this section has examined failures of control measures. The practice of not testing a section of overhead line equipment at all before applying earths, AND a switching error OR applying earths in the wrong location or manner is far from the norm, and has no place in a well managed and delivered isolation. When the live-line tester indicates de-energised overhead line equipment, EARTHS will be erected at the locations detailed on the IDF, before the Nominated Person issues individual overhead line permits to each COSS in charge of each workgroup.
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Several companies have improved the control of these activities with the use of Switching Testing and Earthing Details (STED) forms. In addition to the Nominated Person (NP) verbally instructing the Authorised Person (AP) of the required manual switching, testing and earthing activities, they are also recorded on a STED form that serves as a written instruction from the NP to the AP. It is currently considered best practice and is included in the Network Rail NP&AP training package. During 2005, use of the STED form became mandatory when it was included in Network Rail Company Standard RT/E/S/29987.
4.5
Issue of Overhead Line Permits
The briefing and issue of overhead line permits is intended to safeguard the electrical safety of the recipient. The nominated person must make sure that the COSS understands the following, extracted from Module AC2, section 7 of GE/RT8000: The working limits on the overhead line permit; Where live equipment is adjacent to, or crosses over earthed equipment, exactly which equipment is live and which is earthed; The issue of the overhead line permit does not mean that train movements are stopped on the lines concerned. There is need for time, maturity and professionalism in this process, both by the Nominated Person giving the initial briefing to the COSS, and by the COSS to his/her work group. Factors that influence the efficacy of this information transfer include: Maturity of personnel Role specific competence Number of persons being briefed Number of overhead line permits to be issued Speed – driven by time available and operational pressures Thoroughness of pre-work planning: o o o
Were the number and recipients of Permits identified in advance? Had an isolation walkout taken place? 1 Had a pre-possession site meeting taken place? 2
Does the COSS understand the briefing that he is given? It is the duty of the Nominated Person to ensure that the COSS fully understands it; but the knowledge of the COSS together with the factors above, directly affects whether information is absorbed and understood or only a façade of understanding is thrown up by the COSS: o o
Whether the COSS includes the permit details in the briefing of his/her work group. Whether the relieving COSS is briefed thoroughly and effectively by the COSS he is relieving. There is a risk of the details and importance being diluted or even lost at this secondary and ongoing transfer.
1 The Nominated Person should undertake an isolation walkout in daylight hours to check access arrangements, earth locations and switching locations, and to identify 25 kV residual hazards at least once before any series of isolations in the same area. 2 A pre-possession site meeting enables the isolation provider to meet a representative(s) of the parties requiring Overhead Line Permits, confirm contact details, times and meeting points and if possible show the COSSs the 25kV residual hazards in daylight hours.
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4.6
Hazard from 25kV overhead line equipment
The hazard presented by live overhead line equipment is always life threatening and this hazard remains whilst working in an isolated area, but the briefing, understanding and compliance with an overhead line permit reduces the risk to an acceptable level. The reduction or elimination of residual 25kV hazards is a practical step in reducing the overall risk, regardless of the quality of the overall briefing process. The residual risk from equipment remaining ‘live’ is a factor of the physical arrangement of electrification equipment within, and adjacent to the isolated area, and the coverage of the planned isolation
4.7
Typical residual 25kV hazards Adjacent overhead line equipment remaining alive Section insulators Span wire insulators Back-to-back registration insulators 25kV feeds approaching or crossing over the isolated equipment The live overhead line equipment that abuts the extremities of the isolated area
Note:
The Nominated Person does not usually include Red Bonds in his brief, as they are a dayto-day electrical hazard included in PTS/COSS courses, not a residual 25kV hazard. Disconnection of Red Bonds and other traction bonding MUST be considered when planning track renewals or modifications in order to maintain the integrity of the OLE earthing.
These are the hazards that the Nominated Person should brief and make aware to the COSS, but the need to brief these items depends entirely on whether they are present. Each COSS will have an accepted method statement and risk assessment for his work, but these documents will generally only consider the basic need for overhead line isolation, and not include the danger from specific residual 25kV hazards. This fact indicates the particular importance of the Nominated Persons brief, and the COSS in turn briefing his workgroup. The overriding principal to be employed is to remove the person as far as is practicable away from the hazard, rather than understanding the hazard explicitly and keeping clear of it. This is an important point as it demonstrates safe conditions may appear to be robustly achieved but in reality are much less robust, being reliant on the work activity of the COSS. To measure this reliance, a practical check would be to ask any individual on-site: •
What overhead line equipment adjacent to this isolation is still live at 25kV?
Only face-to-face questioning can prove whether the individual has received and retained this information. Expanding on each 25kV residual hazard listed above: 4.7.1
Adjacent overhead line equipment remaining live
In a multi-track area, all roads are not necessarily isolated simultaneously just to allow work on a single road. Other tracks may remain energised for operational requirements. Therefore, at some stage work will be carried out with the adjacent road alive. This is particularly true on sections of two-track railway where rules-of-the-route only allow single road possession and isolation. In multi-track areas it may be possible to work on an outer road and have the adjacent road deenergised only (isolated but no permits issued), but for maintenance work it would be more likely to take advantage of this availability and issue overhead line permits for both roads enabling work on each. That would mean personnel were again working adjacent to a live road. It should be stressed that it is possible to work with all roads isolated where this is planned with sufficient notice. Depending on area and line, this may be allowed under the rules-of-the-route or may
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require an abnormal possession and isolation. In the latter case significant notice periods have to be given, typically 26 weeks or more. 4.7.2
Section Insulators
If there is a wired crossover with a section insulator in the isolated area and the adjacent road is not part of the isolation, one side of the section insulator will be de-energised and the other side will be energised at 25 kV. It is not usually possible to quote an overhead line structure for this crosstrack isolation limit. The nominated person is required to reach a clear understanding with the COSS regarding this residual 25kV hazard. If the job can be planned so that both roads and electrical sections are included then this hazard can be removed but as previously stated, this may lead to the introduction of other residual 25kV hazards.
Example of High Speed Section Insulator (HSSI), giving rise to live 25kV equipment approaching isolated area
Figure 1 HSSI 25kV residual hazard
Back-to-back registrations and span wire insulators are other physical overhead line features that will approach the isolated area in the across track direction that need to be considered within the NP briefing to the COSS, and the COSS briefing his own work group. 4.7.3
Back-to-back registrations Example of back-to-back registration giving rise to live 25kV equipment approaching isolated area
Figure 2 Back to back registration 25kV residual hazard
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4.7.4
Span wire insulators
Example of span wire insulation live 25kV equipment adjacent to isolated area (The outer span wire insulators have been moved away from the structure face to the platform edge to remove live equipment from above the platform).
Figure 3 Span wire insulator 25kV residual hazard
4.7.5
Live feeds crossing the isolated area
It is common for structure-mounted transformers to be fed from a different road than that to which the structure is adjacent, where each road is a separate electrical section. In practice that means a section of overhead line can be isolated and earthed with live 25kV feeds crossing over the top of it. In headspan construction the demarcation provided by the boom or twin track cantilever (TTC) is absent. Modern designs ensure that the cross track feed is screened and/or 2.75m above the catenary of any separately sectioned OLE. It remains a 25kV residual hazard, particularly the area around the transformer bushings and older types of electrification equipment that were not constructed with the above safety considerations.
Example of live feed able to cross an isolated area giving rise to live 25kV equipment being above and adjacent to the isolated area
Figure 4 Live feed crossing isolated area 25kV residual hazard
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4.7.6
Live equipment that abuts the extremities of the isolation
At one or both ends of the isolated area, live equipment at 25kV will abut. The isolation instructions are written so that it is never possible to work right up to live equipment in the along track direction, there is always an area that is de-energised (minimum 2.75m typically 50m-75m) that will never be included in the limits of the Overhead Line Permit. For instance: At a switched insulated overlap, the limits for the adjacent electrical sections should be one span inside the isolated area, away from the twin cantilever structures forming the overlap
Insulated overlap
Limit of isolation
Limit of isolation
To work in this area, both electrical sections are required to be isolated and earthed and an overhead line permit issued. Figure 5 Insulated overlap isolation limits
At a neutral section the isolation limit is not the centre of the neutral section, it should be one span inside the isolated area in both directions.
Limit of isolation
Neutral Section
Limit of isolation
To work in this area, both electrical sections are required to be isolated and earthed and an overhead line permit issued.
Figure 6 Neutral Section isolation limit
At a switching structure with section insulator, the switching structure is not quoted as the isolation limit it should be one span inside the isolated area in both directions. As a minimum, live equipment must not approach closer than 2.75m to the isolation limit structure, in the along track direction. A particular along track hazard occurs when adjacent roads are not sectioned at the same point in the along track direction, and it is possible to quote a different isolation limit for each road. The affect is that an overhead line permit may safely include one road, whilst the same along track point on the adjacent road will be live at 25kV and therefore not included in the working limits of
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the permit. It is not standard practice to construct or section the overhead line in this way but instances do occur. To avoid this dangerous situation it is normal practice to foreshorten the longer isolated section in the isolation instructions so that the isolation limits are the same on both roads. Any lack of uniformity or clarity with adjacent along track limits raises the likelihood of misunderstanding and an injury or fatality to staff.
4.8
Planning and 25kV Residual Hazards
Standard possessions are in accordance with the rules of the plan/rules of the route. The resultant isolations and 25kV residual hazards are a function of this, rather than the reduction of 25kV hazards being the driving force. This may be a realistic position to take based on train movements being the overriding need, but it leaves a disconnection between regular possession planning and the reduction of 25kV hazards. Based on the low number of fatalities or serious injuries to staff due to electrocution this stance has not triggered numerous electrical accidents. Notwithstanding that, rules-of-the-route possessions (and the isolations matched to them) should still be reviewed periodically to assess the residual 25kV hazards. Abnormal possessions should be booked only after considering which overhead line equipment needs to be made safe for the programmed work, including the reduction or elimination of 25kV residual hazards.
4.9
Hazard and Risk-Based Briefing
The nominated persons briefing should include the electrical hazards present as described in the previous sections. The particular risk of any uncontrolled event happening should be covered in each COSS’s risk assessment attached to the method statement or work planning package for any particular work activity. The NP will not have been involved in the preparation of these risk assessments, nor will he generally have visibility of them. The practical way to avoid this disconnection is to have a pre-possession site meeting to understand the proposed work activity and to match the extent of the isolation to it. A nominated persons briefing for an isolation adjacent to an energised road will have several 25kV residual hazards to brief out. This should attract the highest standard of briefing and level of understanding reached with the COSS, and from the COSS to the individuals in his workgroup. In contrast, a two-track railway with both roads isolated and no residual 25kV hazards presents few electrical hazards to brief out. The standard of the briefing should be of no lesser standard, but fundamentally, there is less electrical hazard information to convey. An obvious but important fact is that the hazard is lower if work is being undertaken in an area completely isolated and earthed. This last condition is rarely reached as there will still be equipment energised at 25kV at one or both ends of the outer track limits of the isolation, but this can be achieved where the limits on the o line permit are several spans within the overall isolated area in all directions. The reduction or elimination of residual 25kV hazards is a practical step in reducing the overall risk, regardless of the efficacy of the overall briefing process. There is an associated risk that staff working for extended periods in isolated areas where no residual 25kV hazards are present, will become complacent to that danger. If they move to work in an isolated area where there are numerous residual 25kV hazards present, any complacency will modify their perception and reduce awareness of the hazard that equipment remaining live at 25kV represents. The Nominated Person will strive to deliver a thorough and effective brief in a professional manner, but has no influence on the selection of COSSs who work in his/her isolation.
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4.10
PTS Electrification Training
The electrification content in the AC module of personal track safety training should be sufficient to arm the successful candidate with basic knowledge of overhead line terminology and safety. This content has been similar for many years. A review should be undertaken of what the candidates are expected to know compared to the suitability of the training material to convey this.
4.11
COSS Electrification Training
Any person(s) identified to receive overhead line permits must hold current COSS competence. Experience has shown that the depth and content of the electrification training within the COSS course can be bettered, particularly in the area of understanding, controlling, and briefing the overhead line permit. The COSS is required to include the permit details in his own brief to his workgroup and furthermore each COSS (when and if relieved) is responsible for briefing the relieving COSS. This requires complete understanding of the overhead line permit in order to brief the next COSS accurately and confidently. There is a risk of the detail and importance being diluted or even lost at this secondary and ongoing transfer. Several companies have run local training sessions to reinforce the roles and responsibilities of a COSS when receiving an overhead Line Permit. Network Rail is in the process of enhancing COSS training in the areas highlighted above. An implementation date should be published.
4.12
Nominated and Authorised Persons Competence
From 2003, Network Rail and industry wide stakeholder groups overhauled Nominated and Authorised Persons training and assessment completely. Individual company training plans with numerous examining and issuing officers appointed regionally by Railtrack or Network Rail have been replaced with one national scheme. Licensed trainers deliver universal and comprehensive training material and examinations, followed by a formal mentoring period during which the successful candidate has probationary status only, and must be accompanied whilst undertaking AP or NP duties. The assessment process commences with an initial assessment during the probationary period, which, if satisfactory, enables the candidate to achieve full status and work without being accompanied. Ongoing workplace assessment, refresher training, and recertification are then embarked upon. In between assessments, the candidate has to demonstrate that he or she is actually undertaking the duties of a Nominated or Authorised Person by keeping a logbook of completed isolation duties. This has been successfully implemented since 2004 and is subject to regular review. It has raised the profile of the Isolation activity and the overall quality of training and assessment. All candidates are subject to ongoing assessment, refresher training and recertification training. This is a positive practical step to improving and maintaining the competence of Nominated and Authorised Persons.
4.13
Compliance with Isolation Procedures
Management of workforce competence is connected to minimising the gap between 100% compliance with standards or procedures, and actual operational practices. Human factors in this equation are looked at elsewhere within this project. The safety and professional culture of any organisation driven from top-to-bottom affects the actions of the workforce delivering the activity. This is underpinned by high standards of initial training and assessment, and managers, supervisors, and peers reinforcing this culture. In other words, other workers and their supervisors do not tolerate malpractice - malpractice is eradicated. In order to identify variations with laid down procedure, the whole isolation process should be subject to regular vertical audits across several territories. Each audit should start with the isolation request through planning to the issue and understanding of the overhead line permit(s) on site.
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Network Rail undertook a national audit of operational isolation procedures for AC & DC electrified lines in 2005, the summary of which was published in October 2005. Minor differences to the isolation forms and electrical control room procedures remain but Network Rail is aware of these issues and is positively working towards standardised electrical control room instructions and forms across the network.
4.14
Isolation Planning
RT/E/S/29987 Module 6 states that the Network Rail isolation planner shall record each overhead line permit requested and allocate each one a unique reference number on an Isolation Planning Form (IPF). A proforma IPF is printed in Module 6 but as this activity is normally PC based and an ongoing activity, it will probably be customised in some way. Whilst it may be possible to identify the number of permits required from the outset, this information is typically not identified until much later in the planning process. This is often in the few weeks preceding the isolation (see Appendix A Possession Pack WON 38, Item 117) or in some cases may not be provided at all (see Appendix B Possession Pack WON 47, Item 05). This non-compliance requires the purpose of the IPF to be reviewed. For example instead of allocating a unique reference number to individual permits, allocate a reference number to each worksite limits/Form B requested and then the permits identified later to be issued from any one of the Form B’s will share the same reference number. That would stop long-term non-compliance with, but still meet the spirit of Module 6. The key issue is to build on this by identifying the total number and recipients of permits before the isolation is effected. To ensure compliance with Module 6 it is important that the layout of the IPF and IDF forms are correctly structured to avoid the need for repeated hand written information detailing limits, lines, structure numbers, electrical sections etc. Current layout suggests that the IPF and IDF are biased towards recording working limits rather than numerous individual permits in any case. In June 2005, Network Rail established a sub-group of the 29987 User Group to review Module 6 thoroughly, including the Isolation Planning and Details Forms (IPF and IDF). The group will have a broad range of personnel involved in the planning and delivery of isolations including the author. The requirements of the IPF need to be made clear, and then compliance checked against those clear requirements. In the final production stage of this document, good progress is being made in this area of isolation planning on parts of the West Coast Main Line (WCML) and the Great Eastern (GE) lines from London Liverpool Street. The 29987 User Group is re-writing many parts of Module 6, considering the removal of the IPF as a paper form ready to be re-issued during 2006. It is essential to understand that many of the issues highlighted in this report are current and ongoing.
4.15
Alternative Methods of Issuing Overhead Line Permits
(RT/E/S/29987 Module 6, section 4.8 February 2005 refers) On major railway renewal or project sites, more than twenty-five COSSs may require overhead line permits, typically within thirty to sixty minutes of the possession being taken. The standard method of issuing permits was not written around that required volume. Notwithstanding that fact, it is the challenge regularly presented to many overhead line Nominated Persons. To ease this demand some individuals explored headroom available in the definition of ‘blockade working’ (pre February 2005 revision of RT/E/S/29987) and only issued an overhead line permit to the Engineering Supervisor (ES). It is worth noting that during the British Rail era (before the creation of the COSS role), if the overhead line function was carrying work out alone, it was common that the permit would be
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issued to the Engineering Supervisor only. He was generally the supervisor of the overhead line works as well. This was undertaken safely on one particular site in East Anglia (see Her Majesty’s Railway Inspectorates (HMRI) report 220002878/RSC/03-04/5.1, which contains much useful information on the management and observation of isolation procedures). At Marston Green on the WCML near Birmingham, the management of the overhead line permit was linked to an electric shock injury and a Prohibition Notice (serial number P/UA/20030702a July 2003) was issued on the construction joint venture alliance comprising Balfour Beatty Rail Projects and Carillion. Network Rail was issued with an Improvement Notice (serial number 1/0782004 dated 7th June 2004) in connection with the same incident. The effect of the Prohibition Notice was to stop the issue of an overhead line permit to the ES only as this was in contravention to the rulebook, then GO/RT4100 (section Z part 1). The Improvement Notice required that any Network Rail Company Standard specifying safe systems of work at or near 25kV OLE is clear and unambiguous with respect to people’s roles, responsibilities and all arrangements for issuing overhead line permit. Furthermore, the procedure described should be robust to prevent abuse and allow for monitoring to check effectiveness, and be able to be practically implemented on-site. Planning was required to be in accordance with Module 6, or if alternative methods were applied, they had to meet the requirements of the previous two sentences. This led to Network Rail introducing Module 6 section 4.8 with respect to alternative methods of issuing overhead line permit. This does allow for the single issue of an overhead line permit but the planning and implementation of this method is particularly stringent. The electrical safety of all individuals on site must be ensured. Please refer to RT/E/S/29987 Module 6 section 4.8.
4.16
Identification of Overhead Line Permit Recipients
This topic was introduced in Isolation Planning. If actioned correctly, it ensures that the Nominated Person knows in advance the total number of permits he has to issue, and enables the NP to establish contact with all the COSSs identified. The early identification of the number of permits is also required to consider whether an alternative method of issuing the permits is selected and implemented. If the number of permits is not identified the trigger to consider whether an alternative method of issuing the permits is selected and implemented will be missed, thus eliminating the chance of planning an effective ‘alternative’ method of issuing the permit. The Nominated Person on the night is then faced with issuing a previously unidentified high number of permits expected in the usual short time to enable work groups to start. Something will flex, namely the chance for the Nominated Person to give an effective individual briefing to each COSS. It is for that express reason that the alternative option has been introduced. It is entirely appropriate to plan how twenty-five COSSs and their workgroups will be effectively briefed in half an hour for instance, rather than hoping the Nominated Person will somehow achieve that on the night. Not identifying all COSS names is a serious omission.
4.17
Over Issue of Overhead Line Permits
This problem relates to the erroneous issue of permits to either COSSs whose work activity does not require an isolation, or to Machine Controllers who are members of a COSS workgroup and not undertaking the COSS role themselves. It seriously devalues the permit process as it destroys the link of proper risk assessment of the work activity driving the need for a permit, and in the latter case can confuse the responsibility of the COSS to brief his group regarding the contents of the permit. He should not expect Machine Controller(s) for whom he is responsible to be in
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possession of a separate permit! In plain terms, it can also render the permit ‘as just another piece of paper’, for those that did not need it in the first place. Factors that have contributed to this practice include: Misinterpretation of GE/RT 8000 (Module AC2, 7.1) - ‘…. the nominated person will hand to each COSS of each work group requiring the isolation, a separate overhead line permit…’ Inexplicably the words ‘requiring the isolation’ appear to be ignored by some readers leaving ‘each COSS’ Confusion with a Machine Controller always requiring COSS competence but not necessarily undertaking COSS duties on any given worksite The Prohibition notice issued to the construction joint venture alliance comprising Balfour Beatty Rail Projects and Carillion (serial number P/UA/20030702a) which prohibited - ‘Work on or near overhead line equipment that requires an isolation, unless every Machine Controller/Controller of Site Safety in charge of an affected work group is provided with a separate overhead line permit (Form C) by the Nominated Person as detailed in the Rulebook GO/RT 4100 (section Z part I)’. This was applied by issuing every Machine Controller with a permit, regardless of whether they were undertaking COSS duties or were already in a COSS’s workgroup Lack of proper identification of permit recipients either because this activity was missed altogether, or not based on risk assessment: both leading to a ‘cover all’ over-issue approach being adopted. The Nominated Person would have to issue more permits than necessary either on a planned basis or in the worst case having to issue permits as required to an unknown number of recipients ‘on the night’. Issuing a high number of permits in a timely fashion severely stretches the ability to use, whilst remaining compliant, the traditional method of briefing and issuing to individual COSSs, adding staff that in fact did not require a permit only makes this problem worse! The option of applying an alternative method of issuing the permits is now included in the Feb 05 revision of RT/E/S/29987. It will require the number of permit recipients to be identified well in advance and the alternative option deliberately selected and implemented.
4.18
The Origin and Purpose of the ‘9 foot rule’ (sic)
In recent history, the distance of 2.75 metres or 9 feet has been used as a safe limit of approach towards live OLE without reference to the electrification department. The selection of this particular distance is now difficult to substantiate but as an example, the following is an extract from the 1975 version of BR 29987 Working Instructions for A.C. Electrified Lines: ‘Work may also be performed in situations other than those referred to above, without reference to the Electric Traction Engineer or equivalent officer, provided the work does not require any part of a workman or any tool or materials which he has to use to approach nearer than 9 feet (2.75 metres) to the live equipment, or provided the work is to be performed by specifically authorised staff.’ It should therefore not be considered as an electrical clearance as such, but a formulaic distance judged to be a safe working distance to allow a worker to approach live OLE without reference to the local overhead line depot. On this criterion, any reduction to less than 2.75m would be difficult to substantiate 3. The ‘9 foot rule’ should not be read in isolation as other text describes how this distance may be infringed with other controls applied. BR 29987 allowed this form of working through the ETE 3 European Standard Technical Report – Annex CLC SC9XC WG 14, dated April 2005 has considered the dimensions equivalent to 2.75m and 600mm in the UK and has derived them to be 1500mm and 500mm using objective criteria. The author has commented on this document and ‘Clearances and screening of live parts, according to EN 50122-1’ to RSSB separately.
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department assessing all factors and nature of the work, and then prescribing one of three solutions: Specified demarcation line (to work up to) Temporary screening (a rigid barrier) Only work under the protection of an overhead line permit (OLE isolated and earthed) Under no circumstance could work take place within 600mm of live OLE. RT/E/S/29987 Modules 2 and 3 developed this principle further with written method statements and risk assessments required, based on whether work was to take place up to 2.75m, or within 2.75m up to 600mm. Authorisation of the method of working is prescribed in Module 3. The COSS must be in possession of the accepted method statement and risk assessment, understand them and critically enact the mitigation measures described. (Railway Group Standard GE/RT 8024 “Persons Working On or Near to AC Electrified Lines” refers.) Considering the 9 feet dimension in electrification schemes pre-1967, working instructions generally forbade staff to climb higher than the footplate of a steam locomotive. The distance from the footplate (the ‘standing surface’) to the overhead line contact wire (at minimum height) is approximately 9 feet. This standing surface clearance to live 25kV equipment is in EN 50122-1 (see section 4.20 of this report) and in RT/E/S/29987, relating to the unloading of wagons (module 3 section 9). In this latter application, 9 feet is not specifically quoted, rather the maximum height of the wagon floor above rail level (1.4 metres). Adding 2.75 metres (approx 9 feet) to this dimension results in a very close approximation to minimum allowable contact wire height. Thus, the 1.4m dimension appears to have been derived from minimum contact wire height minus 9 feet. Ultimately, 9 feet (2.75 metres) has been and continues to be applied in two different ways. There is no direct link between each application. The application to risk assessment in RT/E/S/29987, derived from the previous BR instructions, is the more widely held understanding of what the 9 feet rule means.
4.19
25kv Electrical Clearances to Members of the Public on Station Platforms
This previous section detailed the misconception that it is forbidden for any member of the workforce to approach within 2.75m of live OLE, where in reality they can, with the appropriate control measures. Drawing number CH/EMP/05/001 considers 25kV electrical clearances to members of the public on station platforms. The individual sketches are based on nominal and normal minimum contact wire height (lower contact wire heights exist on certain routes but normal minimum is representative for the UK rail network). There is no special criterion for contact wire height in station platforms. It can be seen that unless passengers stand back from the platform edge as shown in column three, the 2.75m dimension is infringed in each case, perhaps surprisingly so in some of the scenarios shown. In contrast, analysis of electrical injuries to members of the public in 25kV electrified station areas should occur before considering these clearances as unacceptably small.
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4.20
Clearances to Members of the Workforce and Public in EN 50122-1
The following extracts from EN 50122-1:1997 section 5, ‘Protective provisions against electric shock in installations for nominal voltages in excess of 1kV a.c/1.5kV DC up to 25kV AC. or DC to earth’ should be related to the previous two sections: Extract 5.1.2.1-Standing surface ‘For standing surfaces, accessible to persons, clearance for touching in a straight line shown in figure 14, shall be provided against direct contact with live parts of an overhead contact line system as well as any live parts on the outside of a vehicle (e.g. current collectors, roof conductors, resistors). The clearances given in the following clauses are minimum values, which shall be maintained at all temperatures and with additional and exceptional line loading. Due to national or regional existing practises, greater clearances or smaller mesh sizes may be prescribed by the relevant railway authority.’ Extract 5.1.2.2-Standing surfaces for working persons ‘The clearances to be observed for persons working nearby energised overhead contact line systems shall be defined in the operational specifications. If operational specifications do not exist, clearances shown in figure 14 or the clearances according to 5.1.3 shall be used.’ As operational specifications do exist in the United Kingdom these would be expected to take precedence. Figure 14 in EN 50122-1 illustrates vertical and horizontal clearances all round the standing surface. Considering the vertical component only, 2.75m is used but rather than the distance from the extremities of the person, tool or material to the extremity of the live OLE, to be maintained unless other control measures are applied, it is the distance from the standing surface to the nearest live OLE. Whilst that distance is maintained therefore, a worker* may safely stand on that surface according to this standard. Figure 7 below illustrates this. It appears to allow a clearance without further control measures, which in the UK may only be allowed after a method statement, and risk assessment has been authorised and applied on-site. The universal application and compliance with RT/E/S/29987 (module 2 and 3) across all UK railway functions should be checked before judging this ostensibly less onerous approach. *It is surprising that the UK special national condition quoted in figure 7 allows the 2.75m dimension to be applied to members of the public in the case stated. Her Majesty’s Railway Inspectorate would not permit any live equipment over a platform surface whether at 2.75m or 3.5m (the standard vertical clearance for members of the public stated in EN 50122-1). Insulation would be inserted so that cantilevers or span wires are at traction earth potential over the platform surface, or the support structure may be sited other than in the station platform. This clause may therefore have been sought in consideration of clearance from members of the public to roof equipment (pantograph horn, bushings or bus-bars), but would not be applied in the UK to live OLE over the platform standing surface. (Please refer again to CH/EMP/05/001.) Nearest
live
25kV *
920 mm (indicative) 2.75m 1.83m Standing surface
EN 50122-1:1997 Annex G (normative) Special national conditions Clause 5.1.2.1 ‘The dimension of R3.5 mm (sic) clearance in public areas shown in figure 14 shall be amended to R2.75 (sic) minimum for use in the case of future electrification of existing railway lines with restricted infrastructure clearances
Figure 7 Vertical clearances to accessible live parts up to 25kV (based on EN 50122-1)
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Note:
The dimensions of 1.83 m and 920 mm have been added as an example based on the typical height of a male individual.
4.21
Electrical Clearances to Earth
Electrical clearances to earth for single-phase 25kV AC OLE are detailed in many separate UK documents including: Railway Safety Principles and Guidance Part 2 section C Railway Group Standard GE/RT 8025 Electrical Protective Provisions for Electrified Lines Network Rail Company Standard NR/SP/ELP/27214 Maintenance of Mark IIIB Overhead line equipment (formerly EHQ/ST/O/003) BR 12034/16 Railway Electrification 25kV AC Design on B.R. (historical document) The latter document states: ‘British Railways electrical clearances were originally based on the UIC* recommendation and for 25kV were 270mm static clearance and 200mm passing clearance, requiring total headroom above kinematic load gauge at a support point of 680mm’. *International Union of Railways In 1962, following tests and service experience, the statutory clearance requirements on BR were revised and reduced clearances of 200mm static and 150mm passing as were introduced for 25kV operation. These reduced requirements, together with modifications to the design of the overhead equipment, meant that the minimum headroom could be reduced by 175mm and this significantly reduced the costs of obtaining electrification clearances. Research and development work had also established that where insufficient headroom is available to allow the normal catenary/contact wire arrangement, a “twin contact wire” arrangement where the catenary is replaced by contact wire and the two contact wires are supported side-by-side, gave good current collection even with the most restricted clearance arrangement at bridges. A key factor in perfecting the twin-contact wire arrangement and so reducing the headroom for 25kV equipment was the development of large resin-bonded glass fibre rods with track resistant surface covering, which provided a flexible and virtually indestructible combined insulator and support for the twin-contact wires. In 1974, design effort was concentrated on the investigation of possible further reductions in electrical clearance. The objective set was that any improved arrangement must not degrade the surge and 50Hz voltage withstand levels achieved with the existing arrangements. It was found that these levels were governed by the electrical stress between the live end fitting on the equipment support arm and the roof of the bridge or tunnel. This fitting was re-designed to a semicircular shape, to distribute the stress evenly. The re-design of the fitting has enabled the clearance above the live end fitting of the support assembly to be reduced to 95mm static and 70mm passing. At the same time, the passing clearance from the contact wire to kinematic load gauge was reduced to 125mm. These “Special reduced clearance” arrangements mean that a total of only 375mm of headroom is required above kinematic load gauge for 25kV equipment, an additional 25mm being allowed for increased uplift of the contact wire at speeds above 60km/h. Special reduced clearances are adopted in all cases of exceptional difficulty or expense in obtaining greater headroom’
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4.22
25kV electrical clearances to earth summarised:
These clearances are shown in all the documents listed in 4.21, but with some variation, as shown in the tables below: Network Rail Company Standard & BR historical document Category
Static
Passing
Normal
270 mm
200 mm
Reduced
200 mm
150 mm*
Special reduced
150 mm+
125 mm*+
Document NR/SP/ELP/27214 BR 12034/16 NR/SP/ELP/27214 BR 12034/16 NR/SP/ELP/27214 BR 12034/16
* A passing clearance of 80 mm applies to brick and masonry overbridges and tunnels between pantograph and bridge only (not between equipment and bridge) and each case is subject to special dispensation by the Department of Transport. + Where stress-graded glass-fibre bridge arms are used, a static clearance of 95 mm and a passing clearance of 70 mm between the insulator live end casting and bridge are allowable, with special dispensation from the Department of Transport. Group Standard Category Enhanced Normal Reduced Special reduced*
Static 600 mm or greater 599 - 270 mm 269 -200 mm 150 mm
Passing 600 mm or greater 200 mm or greater 199 - 150 mm 149 - 125 mm
Document GE/RT8025 GE/RT8025 GE/RT8025 GE/RT8025
*The values for pantograph to masonry and stress-graded arms are not explicitly stated. Railway Safety Principles and Guidance Part 2 Section C Category
Static
Passing
Document
Normal
200 mm
150 mm
RSP&G ‘C’
Special reduced
150 mm
125 mm
RSP&G ‘C’
Only two categories are explicitly stated.
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5 Consideration of DC Third Rail Isolation and Earthing Processes The original remit and scope of this study was to consider all types of electrification in use on the network of Britain’s railways. However, the situation in respect of isolation and earthing processes on the DC third rail system remains in a state of flux whilst discussion and agreement on the most suitable way forward are resolved between the HMRI, Network Rail, and RSSB. The current standard covering the requirements for isolation and earthing are covered by DC Electrified Lines Instructions GO/RT3091 Issue 2 1998. This standard was developed following the issue of an improvement notice on the then Network South East Division of British Rail by HMRI. In the period from August 1998 to August 2001, much work was done on the production of a new revised document Issue 3. The main differences between Issue 2 and Issue 3 were enhanced requirements to undertake risk assessments of any proposed work in relation to the danger from exposed live parts of electrical equipment. The standard placed an increased emphasis on any work that was likely to come within 300mm of any exposed live parts of the electrical equipment and called for a method statement to be produced by a competent person who must be a member of an organisation holding a valid Safety Case or a valid Contractors Assurance Case. The competent person was required to describe in the method statement how the intended work was to be carried out, without coming into contact with live parts of the electrical equipment. The standard also set down the requirements to submit the method statement for review and acceptance to a competent organisation approved by the Zone Electrification and Plant Engineer (ZEPE). Other principal changes from Issue 2 included: Isolation Agents Temporary Isolations Protective Switch Outs Machine Switch Outs Revised Strapping Arrangements The revised strapping arrangements potentially involved the requirement to fit additional straps and/or straps being placed in close proximity to junctions and incoming supply. Issue 3 of the standard was issued in August 2001 but was withdrawn shortly after issue due to concern from the industry over the increased risk to personnel applying straps from moving vehicles. Much debate has taken place in the intervening period and discussions between HMRI, Network Rail, and RSSB throughout 2006 were aimed at resolving these issues and determining the best way forward. In view of this, it was agreed with RSSB that no further effort would be placed on this aspect of the study.
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6 Human Factor Analysis 6.1
Introduction
This section of the report concentrates on the Human Factors study undertaken as part of the research. It covers the human factor issues and focuses on the human being and their role in electrical safety. 6.1.1
Remit of Human Factors Study
The human factors study set out to achieve the following objectives: Review existing literature to identify any previous work on electrified areas to avoid duplication of effort; Review a sample of railway incidents involving electrified equipment to determine why the people involved behaved the way that they did i.e. intentionally, unintentionally or because of the influence of company safety culture. Prior to gaining access to incident reports, it was anticipated that some time would be available to interview witnesses and persons involved in the incidents to gain a deeper understanding of the behaviours involved. However, due to the volume of information in the reports received and the consequent analysis time required, this was not achieved. It would have been possible to conduct interviews at the expense of the analysis of some of the incidents, but it was considered more important to gather data from as wide a range of sources as possible; Predict the types of human error that could feasibly occur considering the tasks that personnel are required to perform in and around electrified areas.
6.2
Literature Review
A trawl of the human factors literature revealed no previous work explicitly directed towards understanding the human factors issues associated with working in electrified areas in the rail industry. However, some papers covered human factors considerations for railway work in general, including trackside or on-track work. By virtue of the fact that the tasks described in these references could be carried out in electrified areas, they are therefore considered applicable to this project. That is not to say that such tasks would be conducted in exactly the same way in electrified areas (for example, personnel may exercise additional caution whilst maintaining rail in a DC electrified area, and the procedures in place will take account of the additional hazards), however the basics of the task would be very similar. The results of the literature review identified work on the following topics that would be applicable to this project: Safety critical rule compliance; Team-working in the railway industry; Communications errors during track maintenance; Judging distances near overhead power lines. Sections 6.2.1, 6.2.2, 6.2.3, and 6.2.4 provide a brief review of each of these pieces of work, along with their implications for the current project. 6.2.1
Safety Critical Rule Compliance
This work, conducted by Greenstreet Berman for RSSB in June 2004 to address the question of why, although the majority of personnel are conscientious with respect to rules and procedures, incidents have occurred through failure to comply with them. The research investigated the factors
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affecting compliance, the prevalence of non-compliance in the industry, and methods likely to succeed in improving compliance. It also developed a toolkit of practical methods, procedures, and guidance that the railway industry can readily use to improve compliance. The study identified the key influences on safety critical rule compliance as: Organisational factors (e.g. a participative supervisory style was found to produce greater compliance amongst workers, and giving workers health and safety duties was also found to improve compliance levels). Environmental factors (e.g. it was found that the weather and rail conditions can influence whether or not a driver complies with driving rules). Individual differences (e.g. workers were found to differ in terms of their views, for example, on the occurrence of signals passed at danger (SPADs). Some believed they can control SPADs, others believed that SPADs are inevitable, such differences could influence the extent to which individuals are likely to attempt to comply with rules). Cognitive factors (e.g. sometimes tasks can be too demanding for an individual, and hence encourage individuals to decide to ‘cut corners’). Motivations and behaviour (e.g., motivators include performance pressures and peer pressures). Attitudes and beliefs (e.g. individuals may not believe that they are able to comply with formal rules, or they may believe that they do not need to comply with certain rules). Workplace design (e.g., the design of workplaces may provide the opportunity to use equipment in ways that were not intended or may otherwise encourage non-compliance). It was clear from the research performed that non-compliance can be an intentional act (i.e. a ‘violation’ of procedure) or unintentional (i.e. an error). The research resulted in the development of a toolkit for the classification of non-compliance with procedures and understanding why such non-compliances take place. The toolkit also provided users with generic solutions to help encourage compliance, which fell under the following general headings: Enhancing safety leadership behaviours Setting clear standards Making rule & compliance important Supervising & monitoring Applying rewards, sanctions & discipline Improving the rules Making compliance easier / making non-compliance more difficult Education Modifying behaviour Involving staff in rule implementation In terms of the implications for the present study, this work covers both intentional and unintentional behaviours that could result in incidents. It will be beneficial to the project to use the generic solutions to specific types of non-compliance when formulating recommendations during the review of previous railway incidents in electrified areas. The work under the present project is directed towards understanding the reasons for the behaviour that led to a violation or an error, as opposed to understanding the reasons for non-compliance, however, the difference between the two approaches is subtle. It is anticipated that the types of generic corrective actions identified from the previous research into rule compliance will also be applicable to the results of this study.
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6.2.2
Team-working in the Railway Industry
Gregory Harland Limited conducted a 15-month study for RSSB during 2003 and 2004 to develop best practice team-working guidance for the rail industry. The remit of this work was to: Identify areas where teamwork is most critical within the rail industry Determine best practice for teamwork across the rail industry Identify ways of effectively promoting team-working best practice across the rail industry The research work involved studying team-working within the rail industry and identifying important lessons that could be learned from other industries. Using these sources of information as the starting point, the study then worked on the identification of measures of team performance and preliminary guidance on best practice for team-working. The preliminary guidance for teamworking best practice was subjected to a pilot study using a sample of railway group members, prior to being finalised. The study resulted in the development of 20 guidelines for team-working best practice, covering things that individual team members should do as well as things that the organisations should do. The study also resulted in the development of a methodology for assessing both teamwork and the organisational support for teamwork to identify any deficiencies at the individual and organisational levels. The best practice guidelines are easily translated into recommendations for action in order to address any deficiencies identified. A pilot trial of the assessment process and guidelines conducted as part of the study found that the process was readily understood by the participants and provided valuable insights into the current state of teamwork and what was needed to improve it. This study into human factor issues in electrified areas will be focussing on incident reports involving teams of track workers. If any of these incidents indicate a failure in team-working practices, then the best practice guidelines developed under the Gregory Harland study will provide the basis for recommendations for the improvement of team-working. 6.2.3
Communications Errors During Track Maintenance
Gibson et al (2004) used an analysis of recorded voice communications to identify the number of communications errors occurring during track maintenance activities between PICOP / COSS and the signalman. Two types of error were identified: Failure to implement general communications procedures Deviations in information content Each of these error types was sub-divided into a number of specific errors observed during the study (e.g. ‘omission or failure to use the phonetic alphabet’). For each specific error reported, the authors provide an estimate of human error probability (HEP) which is based upon the number of errors observed divided by the number of opportunities for error (based on the total number of times that the relevant task was completed over the course of the period of recording). The results suggested a very high frequency of failures to implement general communications procedures (e.g. failure to use the phonetic alphabet in 78% of cases, not using specific terms (e.g. ‘over’, ‘negative’, ‘disregard’) in 100% of cases.
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The authors suggest that this high failure rate is at least in part due to personnel needing to deviate from the procedures as depicted in the Rulebook, but without support on how best to do this. For example, the Rulebook states that all numerals communicated verbally should be spoken singly (e.g. ‘one’ ‘two’ ‘zero’ as opposed to ‘one hundred and twenty’), but operators find this difficult and confusing when working with longer numerical strings. In addition, the standard terms required in the Rulebook are based upon radio communication, and do not apply to telephone communications (e.g. ‘over’ and ‘out’) hence in communications between PICOP or COSS and signaller, they are not used. Errors of deviation from information content were classified in terms of slips of the tongue. Their frequency was much lower than deviations from procedure. Un-recovered critical slips involving numerical information accounted for only 0.4% of opportunities for error during the observations. The researchers provide evidence from air traffic-control studies to suggest that this figure is consistent with natural human variability in relation to the communication of numerical information. A CIRAS analysis bulletin covering an analysis between June 2000 and February 2002 reports 27 cases of driver-signaller communications failure, approximately 18 of these related to signallers and drivers not responding to each other’s communication. The bulletin cites as a common cause of these errors ‘poor procedures’. This information may provide further evidence for the need to review communications procedures. The Gibson report is relevant to this study in that it is specifically focussed on human errors made during track maintenance tasks. The authors of the reported study state that it would be beneficial to their ongoing research into human error probabilities to examine the occurrence of communication errors that are involved in incident reports. Although this study aims to examine incident reports relating to electrified areas only, the analysis may yield information that is of benefit to continued RSSB research into communications errors. The research by Gibson et al also provides a number of insights into the reasons for noncompliance with communication procedures that could be useful during the investigation of the human factors causes of historical incidents. 6.2.4
Judging Distances Near Overhead Power Lines
There are growing concerns in North America about the risks associated with operating cranes adjacent to overhead power lines. The National Institute for Occupational Safety and Health estimate that around 15 electrocutions every year are caused by contacts between cranes and overhead power lines (mostly power distribution lines as opposed to railway systems, but the principle is the same). A number of standards are quoted which provide precautions or operations near overhead power lines, including OSHA regulations, ANSI standard and the Construction Safety Association of Ontario, Canada’s recommendations for safe working practices when adjacent to overhead power cables. The recommendations from such standards do not provide a great deal of insight into additional means of risk reduction over and above those taken in the UK rail industry. However, some of the suggestions could provide the basis for some recommendations on mitigating risks identified because of the reviewed incident reports, for example: Use of independent insulated barriers to prevent physical contact with overhead cables; Require crane operation at slower than normal speed when under power cables; Raise awareness of the fact that in strong winds cables could sway and reduce clearance between the cable and the vehicle;
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Raise awareness of the need for caution when moving over uneven ground that could reduce separation between the vehicle and the power line. Imbeau et al (1996) also conducted some research into the judgement of clearance between cranes and overhead power cables. A group of 16 trained and experienced crane operators were asked to move their crane hook to the edge of the danger zone around an overhead power cable. They were asked to do this under two conditions: one in which they used no visual aids at all, and simply judged their proximity to the cable. In the second condition, they were presented with fluorescent markers laid on the ground at a distance from the crane representative of the maximum safe extent of the boom in that location. The results of the study revealed that operators were unreliable in judging distance without any reference markers, but when reference markers were provided, operators were much more precise and reliable in judging the edge of the danger zone. As this study involved crane drivers working at a distance of 3 Metres from the nearest live cable it was deemed that this study was appropriate to the research undertaken on this project. The results of this work will be borne in mind whilst reviewing incident reports to determine whether any of the recommendations listed above could be used to help prevent recurrence of incidents involving cranes or other similar vehicles with extendable apparatus.
6.3
Review of Historical Incident Data
This section documents the analysis of 19 incidents involving electrocution or potential electrocution of members of the workforce carrying out work within electrified areas (both conductor rail and overhead line equipment). This work has been supplemented by a predictive analysis of human error risk conducted using the task-based risk assessment in electrified areas conducted for this project and detailed in section 7 of this report. This supplementary exercise of predicting human error aimed to identify all forms of human error that could conceivably occur whilst conducting those tasks represented in the risk assessment. As such, the analysis is less focussed than the analysis of previous incidents included in this section. The results are intended to provide the reader with an indication of what could occur, and the various ways in which these events could come about. A number of recommendations have been made due to the predictive analysis, and because some predicted errors could happen in a number of different ways, these recommendations need to cover all possible ways in which an error could occur. Because the events are predicted, and not identified through the analysis of actual events, these recommendations need to be very high-level, indicating the types of mitigation that could be implemented to prevent the predicted errors, but would need to be put into context to solve specific problems. For all of these reasons we have elected to include this analysis as an appendix to the report, as the recommendations are less focussed than those resulting from the analysis of historical incident data.
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The focus of the work reported here was to identify the human factors lessons that could be learned from previous incidents, and so it is this work which forms the main body of this section of the report. Recommendations emerging from the historical analysis are more directed towards preventing a specific type of event from occurring again, or at least reducing the impact of the event if it does occur. The remainder of this section concentrates on the historical analysis of 19 of serious incidents involving electric shock, electrocution or near misses. These were as follows:
Location
Date
Paddington, Acton East
21 January 2000
Adwick
2 August 2000
Hither Green
25 July 1995
Dock Junction
10 February 2002
Doncaster Belmont Yard
2 December 2001
East Croydon
8 September 2002
Handsworth
5 March 2002
Harlow Mill
5 May 2002
Hemel Hempstead
8 August 2001
Liverpool Street
7 November 1999
Marston Green
1 July 2003
Oakley
7 August 2003
Ranskill
19 October 1998
West Croydon
10 October 2001
Tollerton
2 May 2001
Hooton
5 March 2003
Leighton Buzzard
14 June 1985
Euston
12 November 1988
Hett
14 April 1998
The reports were reviewed using three forms of human factors analysis: human error analysis, ABC analysis of violations, and safety culture analysis. Each of these forms of analysis is described in Appendix C. In a number of cases, incidents did not include just one type of human failure; they tended to have involved both errors and violations, or a combination of errors, or a combination of violations. In some cases, there was evidence to suggest that the safety culture of the organisation that employed the worker had some influence on the incident. Because of project time and budget limitations, given the volume of information included in the 19 reports analysed, this analysis has had to focus on those human failures directly relating to the incident, rather than the indirect failures. Additionally, many indirect failures are not explicitly described in the incident reports. The primary focus is on the immediate cause of the incident, with some description of other causes, but not in sufficient detail to perform a human factors analysis. For example, an incident may involve a violation on the part of a worker who did not follow the required procedure for checking whether a line was de-energised. This would be considered the direct failure in relation to the incident. However, it is also possible that planning errors could have contributed to the incident, but whilst such an error would be acknowledged as having contributed to the incident, these would not be thoroughly analysed.
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This report provides details of the analysis for each incident reviewed, which includes recommendations for addressing similar human factors issues in the future. 6.3.1
Incident Analysis Procedure
The procedure followed when analysing each of the incidents was as follows: 1. Review the incident report and identify the behaviours that were exhibited leading up to the incident. 2. From the evidence available, decide whether the behaviour was intentional or unintentional. 3. When the behaviour was intentional, apply the ABC analysis tool to determine the triggers and consequences for the behaviour, and specify the alternative, safe, behaviour along with required triggers and consequences. 4. When the behaviour was unintentional, apply the human error analysis tool to determine the underlying psychological causes and formulate recommendations for preventing recurrence or reducing the impact of future similar errors. 5. Use the safety culture analysis-tool to determine any possible safety culture influences on the behaviour in question and recommend action as appropriate. In some cases, there was insufficient evidence to identify specific behaviours involved in the incident. In such cases, this was reported as the outcome of the analysis. In several cases, there was evidence of failure in the planning process, and other works management processes that occurred well in advance of the incident itself. In such cases, the nature of these failures could rarely be determined, as the investigations tended to focus on the reasons for the incident itself. However, where possible these problems have been highlighted although it has not been possible to analyse them in any depth. The following sections of this report provide the reader with a synopsis of each incident, the form of human factors analysis applied (i.e. human error analysis, ABC analysis or safety culture analysis) and the recommendations resulting from the analysis of the individual incident. Full transcripts of the human factors analyses conducted for each of the incidents are included at Appendix D. 6.3.2
Difficulties in Analysis of Historical Data
Re-analysing incident reports after the event is often difficult because the analyst is constrained by the information contained within the report, and occasionally has to base analysis on assumptions made by the original investigators. This study was no exception. Information regarding human factors issues associated with incidents tends to require a high level of detail to be reported in the incident report. In some cases, the reports that were available for this study contained little detail; some comprised only a Coroner’s report, which did not provide any information on what actually happened at the time of the accident. In cases such as this, where there was plainly insufficient information to conduct an analysis, this is stated in this section of the report.
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6.4
Results of Review of Historical Incident Data
This section contains a summary of the review of the 19 incidents used in this project. For each incident, a synopsis is provided which summarises the incident and the human factors analyses conducted. Following each synopsis there is a summary of the recommendations resulting from the human factors analysis of that specific incident. These recommendations are analysed to identify common themes in Section 6.5, and the resulting key recommendations are included at Section 6.6. 6.4.1
Acton East 21st January 2000
Synopsis The nominated person (NP) for the isolation was applying earths to an isolated section at a designated earthing point (DEP) when there was arcing across and the earth blew, indicating that the section was in fact still live. It was later found that a switch that was normally open was in fact closed. The NP had conducted live line testing to confirm that the power had been isolated prior to applying the earths, but the tester was found to have been defective. The Live-Dead-Live procedure for live line testing had not been applied. In this procedure, the user tests a known live line, followed by the dead line, followed by a live line. This allows the user to confirm the different deflections of the needle for live and dead lines. The formal investigation report finds that this incident included a trend of failing to follow the Live-Dead-Live testing procedure, resulting in arcing and a blown earth. The human factors analysis of this behaviour suggested that it was possible, given the evidence, that this could have been either intentional or unintentional, and therefore both ABC analysis and human error analysis were applied. It was also noted that what appears to have been a switching error had occurred that resulted in the line, which was expected to be de-energised, being energised. However, the incident report states that the investigation into this error was unable to identify how the switch became closed, and that it could have been closed for up to three months prior to the incident without detection. It was not therefore possible to perform any analysis on this error. The contents of the incident report state that had the Live-Dead-Live procedure been followed, the switching error would have been detected. Analysis Recommendations Raise awareness of the existing procedure that ensures that all live line testing equipment is tested using signage and briefings prior to leaving the depot. Increase the frequency of routine testing. Publicise the results of this incident to illustrate to personnel the potential consequences of not following the correct procedure. Engage some of the personnel involved in relaying their experience of what it was actually like. Apply a label to a prominent position on the live line tester to remind users of the correct procedure. Implement a safety observation scheme to provide praise for personnel seen to be consistently working safely to act as positive reinforcement, and explore the reasons why people do not follow the procedures. These can be used to introduce negative reinforcement for unsafe behaviours. Provide training to all personnel who will act as on-the-job instructors. This should include an assessment of a person’s ability to train another person (it does not always follow that a person good at doing the job will be good at training someone else to do it). Procedure should include detailed information on what to do, and why to do it – procedures often focus only on what is required, knowing why it is required often helps to encourage compliance.
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Instil in workers the importance of checking all information available before coming to a decision. Decision-making training may be appropriate for NP level personnel. Another high potential risk scenario was introduced when the NP was supervising a trainee. There are a number of examples of historical incidents where this situation has been shown to contribute to poor performance of a primary task. For example, research in air traffic control revealed a higher than average number of incidents when experienced air traffic controllers were mentoring a trainee controller. In such cases, the underlying causes were to do with a need to divide attention between a primary task and a similar secondary task, and the effectiveness of training provided for mentors. Taken in conjunction with the ongoing maintenance work, these two factors may have had a significant impact on performance at the time of the incident. Awareness should be raised of the conditions where performance and communications can break down, and when to pay more attention to the procedures. 6.4.2
Adwick, 2nd August 2000
Synopsis Whilst cutting back a bush, which was getting close to the return conductor, a worker carried cut branches to an overgrown area and threw one from above his head to get it well into the overgrown area. The tip of the branch brushed the tail wire on the OLE, resulting in a mild electric shock. Review of the incident as part of the human factors analysis revealed little in the way of detailed information to make a clear distinction between intentional and unintentional behaviour, hence both ABC analysis and human error analysis were applied. The absence of briefing on the electrical hazards associated with the work was also a factor, but details of the COSS actions are not available to allow any analysis of the associated behaviour. A formal investigation report was not available for this incident. A copy of a three-page internal fax, which contains the internal investigation report (a brief description of the incident and the investigation conclusions and recommendations), was used. Analysis Recommendations Provide all OLE workers with a safety induction briefing or formal training in the hazards associated with overhead lines. Provide a rule of thumb to workers to indicate what is a safe distance from the line (i.e. nothing to be held above head height). Check the effectiveness of training and mentoring to ensure that workers are going onto the railway line with the necessary information, paying particular attention to new recruits. Use videos to show graphically the consequences of contact with the OLE. 6.4.3
Hither Green, 25 July 1995
Synopsis A track worker fell with his chest across the conductor rail with no protective equipment worn above the waist. The result was electrocution. Witnesses were unable to explain the actions of the deceased immediately prior to the accident, so the behaviours concerned could not be examined in detail. However, the behaviour of not wearing full PPE, which, had it been worn may have reduced the severity of the accident, can be analysed. The deceased was naked above the waist, having removed his high-visibility vest and T-shirt and tied the vest around his waist. Assuming that the victim was aware of the requirement to wear the vest, this was clearly an intentional violation, and was therefore analysed using ABC analysis. Note that direct exposure to the third rail is not considered intentional; there was clearly some unintentional activity which led to contact.
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Additional factors identified in the incident report involve failures to introduce safe systems of work and insufficient planning. In both cases, there will have been behaviours that could have been further analysed, but since they are contributory factors, they are not covered in detail in the incident report. Analysis Recommendations Provide training for how to intervene and accept intervention constructively. Many people have a problem with this, and this is required if people are to feel comfortable intervening. Identify suppliers of more comfortable PPE under all weather conditions and conduct usability trial. Assess safety culture to identify why people do not intervene and encourage managers, COSS, etc to lead by example. Some of these problems may be addressed through training on intervention. 6.4.4
Dock Junction, 10 February 2002
Synopsis A gang of sub-contractors was due to dismantle and remove scaffolding from an area in proximity to OLE under T3 protection. The duration of the possession and isolation were shortened such that there would only be 2 hours to complete the job rather than 4 ½ hours. Three hours were required to do the job safely. Due to the lack of contingency arrangements, the COSS decided to amend the method statement to allow removal of the scaffold before the possession/isolation was granted. This involves contractors carrying scaffold poles above head height. The deputy possession manager intervened to stop this activity until the possession/isolation was confirmed. There were no injuries. This incident clearly involves a violation of the procedures by the COSS and hence ABC analysis only has been used to analyse it. Analysis Recommendations All similar work to be completed only under T3 conditions – reinforce the right to stop work in the event that COSS believes that safety is compromised. If one is not already in place, introduce a scheme similar to “Time Out For Safety” – TOFS) which empowers employees to stop work should they feel that there are any threats to safety. Priority to be given to safety over productivity - managers need to lead by example and not punish the workers if they are unable to complete a job because of safety constraints. 6.4.5
Doncaster Belmont, 2 December 2001
Synopsis A worker was asked to go and find a tank wagon in the yard, which was carrying fuel for the central heating system. He found the tank wagon, which was properly labelled. There were no witnesses to the accident, but the worker had climbed onto the top of the tank wagon and was fatally electrocuted either by contact with or by arcing from the OLE. Due to the lack of witnesses, the report contains a number of assumptions. It is by no means certain whether this behaviour of climbing on to the tank wagon was intentional or unintentional, although it is conceivable that the worker made some form of error in judgement regarding climbing onto the tank wagon. The human factors analysis has proceeded on this assumption. The report suggests that there may have been a lack of awareness of electrical hazards due to the deceased not being issued with Section Z of the Rulebook. There would have been a behaviour
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associated with this failing, but there is insufficient information in the report to analyse this further. The full incident report was not available for review. The information reviewed appears to come from two different sources, and provides a summary of the inquiry and the conclusions and recommendations of the investigation only. Analysis Recommendations All personnel whose work could bring them into an area where live overhead lines are present should be briefed on the dangers of Overhead Line equipment, and should have a copy of the relevant rules and procedures for their personal use. Introduce a procedure for a situational risk assessment when an individual or team of workers come across a task with which they are not familiar. All personnel who may encounter labelling used on goods wagons of any description to be provided with training on their location and meaning. 6.4.6
East Croydon 8 September 2002
Synopsis Whilst fitting plastic tubes around traction current cables with the conductor rail live and the line open to trains, the COSS made contact with the conductor rail and the running rail, resulting in fatal electric shock. There was no evidence to indicate what the COSS had been doing immediately prior to the accident. Given the lack of evidence of the COSS’s actions prior to the accident, detailed analysis has not been possible. However, the fact that a conductor rail shield was not taken to the worksite and that there was no method statement for the job suggests that violations of procedure had occurred, and hence an ABC analysis has been conducted on the incident in general, rather than on the undetermined behaviour of the COSS. The report also indicated behaviours associated with the short-term rather than long-term planning of work. Although these are acknowledged as factors that affected this incident, there is insufficient detail in the incident report to analyse these further. Analysis Recommendations Clarify through procedures, briefings, etc. that method statements for all tasks that bear the risk of electrocution are a requirement, regardless of how simple the task may appear. Introduce a safety observation scheme where an NP would tour worksites on a scheduled basis and provide positive feedback for safe performance, to reinforce safe behaviour. Teams that perform consistently safely could receive some form of positive feedback that is meaningful to them (for example a monthly prize – a night out for example that they can all partake of as a team) or even just recognition through publicising their successes in a popular company journal, on a notice board that is often used, etc. Introducing incentives for meeting safety targets should be discouraged, as it encourages workers to behave safely only when there is something in it for them, rather than triggering a change in their beliefs and values relating to safety. What is recommended here is a reinforcement of safe behaviour rather than an incentive scheme. Introduce regular work audits to allow managers to identify and actively discourage unsafe behaviours, involving those involved in unsafe acts in developing a safer way of working.
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6.4.7
Handsworth, 5 March 2002
Synopsis Whilst erecting fencing in the West Midlands and Chilterns area, and having conducted a CAT scan which indicated the presence of a buried metal object, two workers ruptured a 132kv buried cable, resulting in an explosion and burns to both men. This accident seems, on review of the evidence, to have been the result of an error on the part of the two workers brought about by a number of factors to do with their expectations, the reliability of equipment, and the efficiency of the planning process. A human error analysis was conducted, which is reported below. The formal incident report acknowledges several factors relating to planning of the job, lack of resource, sub-contractor safety assessment, and chain of command all contributed to the incident. All of these will have had behaviours associated with them, but they are not investigated in-depth in the report, hence human factors analysis was not possible. Analysis Recommendations Provide additional methodical checking of the planning documentation and information passed to the work site regarding location of hazards. Introduce procedures to proceed with caution when resistance is encountered when digging, until the source of resistance has been identified. 6.4.8
Harlow Mill, 5 May 2002
Synopsis Two members of staff involved in the renewal of sleepers and ballast were asked to redistribute the loads in three wagons of spoil. The two men climbed into the wagons to redistribute the loads, and on reaching the second wagon, one of the men received an electric shock after coming into contact with live OLE. The human factors analysis of this accident focuses on the behaviours of the engineering supervisors involved, which led to a failure in briefing personnel on the safety aspects of the work. Two behaviours were identified which, based on the evidence presented, appeared to be unintentional, and hence human error analysis has been used to analyse this incident. Other relevant factors included the decision to control a risk using ‘briefing by the COSS’ and the inconsistent recording of the isolation limits in the documentation for the work. Both factors will have involved a human failure or failures, but there is insufficient detail in the investigation report to analyse these further. Analysis Recommendations Conduct regular audits of COSS briefings to determine their quality and provide coaching and development for those that require it. Introduce a procedure that requires systematic checks to be made of the limits of all work areas prior to briefing other personnel. Provide coaching and / or training in how to communicate safety information effectively. Provide guidance on high-risk handovers, and how to reduce the associated risks – this may involve using a checklist, if this is appropriate. Ideally, the procedure for Form ‘C’ acceptance and briefing of COSSs should be consistent across organisations working in rail. To account for the fact that this is unlikely to be the case in practice, site briefings should be provided to ensure that local procedures are briefed to any personnel that have not worked on site before. This should be treated as a site safety induction.
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Indications in this report that there may have been multiple violations on site in failing to follow the procedure to formally brief on the Form ‘C’ contents to COSSs, but insufficient evidence to pursue. 6.4.9
Hemel Hempstead, 8th August 2001
Synopsis A group of workers were performing overhead line maintenance from the top of an overhead line train. A crossover section insulator was close to the train, and workers were warned of this being live equipment. The victim was attempting to clean a section insulator rod when he received an electric shock. He was thrown backwards, onto the train roof, ablaze. It was later stated that no one had asked the victim to clean the section insulator, and that at least one other member of the crew did not know that the section insulator in question was live. The review of the incident suggested that the victim did not intentionally reach out for a live piece of equipment, suggesting that this was an error. It is also possible that an error was made on the part of the person briefing the victim on his tasks; hence, error analyses have been conducted for both possibilities. It is also clear that some form of human behaviour was also associated with the lack of formal training, lack of a method statement and failure to cover electrical hazards fully in the work procedure. However, although these are highlighted as contributory factors in the incident report, there is insufficient detail for more detailed analysis of the associated behaviours. Analysis Recommendations Provide safety communications training to personnel, providing workers with guidance and practice on how to convey safety-related information most effectively in the least ambiguous manner, and to encourage workers on the receiving end of information to check their understanding and clarify any issues they are not 100% comfortable with. See also the recommendations made by Gibson et al (2004) on reducing safety communications errors, which includes a recommendation to improve the usability of existing communications procedures to improve compliance levels. When work is conducted in an area where the complexity of the overhead lines is high, determine the potential benefits of conducting line testing procedures whenever moving to a new piece of overhead equipment. 6.4.10 Liverpool Street, 7th November 1999 Synopsis Whilst climbing scaffolding at Liverpool Street Station in order to dismantle it, a contractor made contact with the overhead line equipment. This resulted in the contractor being thrown backwards onto the track and sustaining injuries due to electric shock and the fall onto the tracks. The human factors review of this incident suggested that the contractors involved might have made an error based upon the manner and content of information provided to them regarding the job. The COSS did not receive face-to-face communication regarding the job, but was briefed over the telephone regarding the track arrangements, and did not gain sufficient understanding of the isolation arrangements from the NP. This was seen primarily as a planning and control of contract issue, and has been analysed using the human error analysis tool. The formal investigation report identifies a number of factors that were not investigated in detail which relate to a failure to follow briefing procedures and differing isolation and possession limits. As these are raised as ‘factors for consideration’, there is insufficient detail to perform human factors analysis on the associated behaviours.
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Analysis Recommendations Worksite and isolation limits to coincide to reduce the risk of confusion. Audits by site safety authority on regular basis to identify problems with briefings or the physical conduct of work 6.4.11 Marston Green, 1st July 2003 Synopsis Overhead line prep work was underway at the accident location. The COSSs had briefed the workers that the overhead lines were not yet isolated and that the Form C had not been received. Road rail vehicles (RRV) were driven onto the road rail access point (RRAP) under live OLE to await the Form C. The isolation was delayed, but some men did not know whether to begin ground-level work under OLE or stay in the cab. One vehicle was set up for control from the basket, when it was necessary to raise the basket slightly to see over the cab. At some point shortly thereafter, a flashover occurred and both men in the basket jumped out of the basket. A human factors review of the incident report suggested that the vehicle was driven down the line whilst the line was still live, indicating an intentional behaviour on the part of the crew. An ABC analysis has, therefore, been conducted. Several other issues were highlighted in the report associated with behaviours prior to the incident. These were the shortening of the isolation limits prior to start of work, documentation references being outdated, poorly written procedures, and poor briefing from the COSS. Although there will have been specific behaviours associated with these events that could have been subjected to human factors analysis, there was insufficient detail in the report to do so. The version of the report reviewed was a draft produced on 18 July 2003, not a formal investigation report. Analysis Recommendations Procedure to state that baskets, or other exterior elevated structures on vehicles, will not be used under live OLE, with a possible extension to this procedure to leave interlock keys for basket operation with an NP or a person who will not be working under OLE and to have them handed back when the Form C is issued. Provide handover and safety communications training to all personnel working in electrified areas to cover principles of accurate and safe communication, including two-way checking of understanding, etc. Some workers reported they were not sure whether they were authorised to start groundwork on arrival (some were instructed to do so by supervisors). Situation not clear, led to assumptions being made. Include in training the importance of use of positive statements in providing information – i.e. state whether or not Form C is present, not that it is expected – either the permit is in force or it is not. 6.4.12 Oakley, 7 August 2003 Synopsis While a gang was replacing broken insulator pots, repositioning displaced pots, and changing pot fixings, etc. a lookout on the job was seen to bend down as if to do some work. Shortly afterwards the lookout made contact with the conductor rail, resulting in a fatal electric shock. A review of the incident suggested that there was some form of violation on behalf of the lookout engaging in work other than the duties assigned to him, and hence an ABC analysis was done. There was also some evidence to suggest that the safety culture of the organisation could have had an impact on the behaviour of the individual, and a safety culture analysis has also been
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completed. It was also noted that a lack of formal training, checking for possessions only one week ahead, and an inadequate method statement were also factors for which there would be a corresponding human behaviour. However, although these are acknowledged in the incident report, there is insufficient detail to analyse them further. Analysis Recommendations
•
•
Conduct regular audits of risk assessments to identify those that focus on high-level risks or hazards, rather than those specific to the job. Work without an adequate risk assessment along these lines should not be allowed. Management to make their expectations clear regarding the quality of risk assessments, and these should be included in the risk assessment procedure. Assess the safety culture of the organisation to determine the impact on safety practices within the workforce. If issues are identified, develop improvement actions to enhance safety culture with the involvement of the workforce. Explicitly state in procedures when a particular method of conducting work is not permitted under company policy, i.e. do not rely on implication. On-the-job training should be conducted either by COSS or by another member of the gang not involved in other duties that could detract from the quality of training provided, or draw them away from other duties, which require their attention. Use a sign-off system similar to the safety briefing to record who provided the training and the confirmation from the trainee that the training has been received. Work planning for electrical work to identify first available T3 possession – planners to be encouraged to look further ahead. Provide negative feedback if T3 possessions were available but not used due to perceived time pressure.
6.4.13 Ranskill, 19 October 1998 Synopsis At about 04:50 on the day of the accident, while disconnecting local earths from an overhead line structure towards the end of an isolation, a linesman received a fatal electric shock because he disconnected the earth end before the line end was clear. Long earths had to be used instead of short earths because the expected DEP was not present at the expected structure. A human factors review of the incident suggests that the most plausible explanation for this behaviour was that it was unintended, and hence a human error analysis has been applied. The lack of a control measure to prevent the possibility of a person applying or removing earths in the wrong sequence, and the absence of a formal audit and inspection system to observe the isolation process were cited as potential underlying causes of this incident. However, there is insufficient information in the report to analyse these in any more detail. Analysis Recommendations Introduce a procedure, which states that when removing long earths, one man removes both the line end and the rail end of the earth. It seems that communication on who was doing which part of the task broke down in this case. Workforce should receive training on effective communication and co-ordination strategies for safety-related activities. See also Gibson et al (2004) recommendations on modification of procedures for safety communication. The workers were trained in the use of long earths, but experience of actually applying them was limited. For safety-related tasks, ensure that practical experience is received within one month of initial training. If the task is not performed for an extended period of time (for example 6 months) then refresher training should be provided, which need not be in the same format as the original training.
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The worker who died had worked 21 consecutive shifts, with two 84-hour weeks immediately prior to the incident. It seems highly likely that this contributed to his performance on the day of the accident. Working hours should be monitored and action taken when an individual worker has exposed themselves to high levels of fatigue that could endanger themselves and their co-workers. Frequent auditing of records should be used to identify problem cases. 6.4.14 West Croydon, 10 October 2001 Synopsis During the course of maintaining a rail flange lubricator, an uninsulated, open-ended spanner contacted the energised conductor rail. This resulted in an arc that caused the grease in the vicinity to ignite, and injure two workers. Human factors review of the incident suggested that this behaviour was unintentional, it was difficult to conceive why someone would do this intentionally and hence human error analysis was conducted. It is recognised, however, that the use of uninsulated tools could be considered a violation, although there was insufficient information in the report to allow full analysis of this. The formal incident report identifies a number of underlying causes, all of which involve human behaviours, many of which involve unsafe behaviour on the part of management. They were: Not providing suitable tools Lack of suitable training in risk identification Failure to enforce procurement policy Conductor rail shield applied incorrectly Failure to obtain method statements and risk assessments Failing to monitor contractors All of these factors involved human behaviour, but there is insufficient detail in the report to analyse them further. Analysis Recommendations The work was carried out without an isolation, which would have prevented the accident. Recommend that where possible, electrical work is conducted under T3 isolation Ensure that properly insulated tools are used in electrified areas. Where T3 isolation is not possible, conductor rail shields must be used as a matter of course. 6.4.15 Tollerton, 2 May 2001 Synopsis As part of maintenance work in the area, a group of contract staff were to unload track from a HIAB crane. The area for unloading the crane was under live OLE, and the HIAB fouled the OLE, resulting in electric shock to some of the men on board. A human factors review of the accident suggested that the crane operator had intentionally raised the crane arm, and hence an ABC analysis was conducted. The formal incident report states that inadequate planning and resourcing of the job was an underlying factor in the incident, but details of the behaviours of those involved in these activities were not included in the report, precluding more detailed human factors analysis.
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Analysis Recommendations Conduct regular audits of work planning to ensure that work, involving vehicles with extending parts, takes place wherever possible under T3 possession. Introduce procedure disallowing any movement of crane arms, etc. when the vehicle is beneath live OLE. Note:
In the formal incident report there is no transcript of an interview with the crane driver, as it is stated that no interview had been achieved prior to publication of the report. The evidence in the report as it stands suggests a violation; however, it would be useful to have had access to more detailed information to determine whether there was also an error involved. Previous work reviewed during this project suggests possible simple systems to help improve the judgement of distance when operating cranes near overhead power cables. If an error in judgement was involved, then these recommendations would also be pertinent (See Imbeau et al, 1996).
6.4.16 Hooton, 5 March 2000 Insufficient information on the actions of the injured party was available for the conduct of human factors analysis. It was not clear whether the behaviour was intentional or unintentional. The lack of clarity is because only information contained in the original incident recording forms and SMIS was available, which lacked sufficient detail to analyse the behaviours involved. 6.4.17 Leighton Buzzard 14 June 1985 Insufficient information was available on what the victim was doing at the time of the accident to conduct any detailed analysis. It is known that the branch that was being cut made contact with OLE because the worker had to cut from one side, then the other with the chainsaw in order to cut through it. Witnesses stated that the saw sounded as if it was labouring, but that the deceased had stated that it was always like that. This suggests inappropriate tools and equipment to do the job. It is possible the incident could have been prevented if the saw was capable of cutting through the branch without having to change position and bend the branch to remove it. Information for this incident came not from a formal incident report, but from a copy of the inquest along with hand-written and typed witness statements, providing little in the way of detail on the behaviour of the deceased or others within the organisation. 6.4.18 Euston, 12 November 1988 The worker did not appear to have been briefed of the hazards associated with trains or overhead lines prior to starting work, and work did not seem to have been monitored. The worker took a shortcut that meant that the metal pole he was carrying made contact with OLE. The deceased was working at the station for the first time, was not an OLE operator, and should have received a comprehensive briefing. Information on this incident came from a copy of the post-mortem examination and a typed transcript of the inquest. 6.4.19 Hett, 14 April 1998 There is no evidence in the report to indicate how this incident happened, as the only witness was the injured party, who was in hospital at the time of the inquiry. None of his co-workers saw what happened. It is therefore not possible to complete a human factors analysis on this incident.
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6.5
Conclusions
The review of incident reports identified a range of behaviours involved in a sample of incidents spanning the last 15 years. The number of intentional behaviours (violations) and the number of unintentional behaviours (errors) were approximately equal with a few more errors identified than violations. In many cases due to the individual dying because of the incident, one can never be positive about the level of intent involved. 6.5.1
Common Causes of Behaviours
The review and analysis of the incidents revealed a wide range of causes for the behaviours that were exhibited, ranging from the physical (e.g. poor lighting) to the psychological (e.g. seeking approval from a manager or colleague). However, there were a number of causes, which were common to many of the behaviours that contributed to, or triggered these accidents, as described in the table below: No. of Behaviours Exhibiting Factor 4
Common Cause Poor risk awareness (including lack of awareness training, or ineffective awareness training) Insufficient briefing (includes not following prescribed briefing procedure) Complacency (for example during longterm non-standard activities such as maintenance or when workers are highly experienced with a task) Working under perceived time pressure, leading to the perceived need to get the job done quickly Seeking approval for getting the job done, or seeking to avoid ridicule for not joining in with custom and practice Lack of (or accessibility of) a specific method statement, risk assessment or procedure for the job Lack of suitable tools and equipment to do the job (including lack of interlocks, poor ergonomic design)
9 8 7
5 5
Associated Recommendation Safety Communications Training Supervisory Checks Safety Communications Training Safety Communications Training Safety Observation Scheme Checking the Planning Process Supervisory Checks Safety Observation Scheme Safety Culture Supervisory Checks
4
Safety Observation Scheme Supervisory Checks
4
Safety Observation Scheme
These common causes should be used to raise awareness within the organisations working on the railways of the conditions and situations under which the risk of a human failure could be increased. The following section provides details of the recommendations that were generated because of the analyses in order to combat the common causes in the preceding table, and provides some indications as to those that are likely to have the greatest effect in improving safe working
4 This is the number of behaviours identified during the incident review and analysis, not the number of incidents. Some incidents involved more than one unsafe behaviour that was the subject of the human factors analyses.
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practices in electrified areas. The links between the recommendations and the common causes are indicated in the above table. 6.5.2
Summary of All Analyses
In coming to conclusions regarding the incidents reviewed, the first stage was to consolidate the number of recommendations made for all of the incidents into a more manageable list. Some recommendations were very specific to one incident; others were applicable to several of the incidents reviewed. Where the latter was the case, these have been merged into a single recommendation that would be applicable to the incidents reviewed. To track this process, a table was created showing all of the incidents reviewed along the top, the recommendations down the side, and tick marks indicating which recommendations were applicable to which incidents. The recommendations have been listed in descending order of the number of incidents to which they apply. In the table, the descriptions of the recommendations have been summarised – for details of the recommendations for each incident please refer to the relevant part of the previous section of this report.
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Hett
Leighton Buzzard Euston
Hooton
West Croydon Tollerton
Ranskill
Hemel Hempstead Liverpool Street Marston Green Oakley
Harlow Mill
Handsworth
Dock Junction Doncaster Belmont East Croydon
Hither Green
Adwick
Acton
Recommendation
Safety communication training to include handovers and how to intervene effectively Safety observation scheme to praise safe behaviour and discourage unsafe behaviour, audit briefings, etc. More methodical checks of planning process, scheduled for T3, limits of isolation Monitor line testing procedures Publicise incident consequences using videos, briefings, etc. Training and procedures for on-the-job trainers Safety inductions that cover generic issues plus dangers of electrical equipment Assess Safety Culture (as required by RGSP). Procedures to discourage extending parts under OHLE
use
of
vehicle
Attach procedural aide mémoire to equipment Rules of thumb for distance judgement Audit training improvements
effectiveness
and
identify
Identify more comfortable PPE for all conditions Introduce a Time-Out For Safety scheme Managers to demonstrate safety more important than productivity
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Hett
Leighton Buzzard Euston
Hooton
West Croydon Tollerton
Ranskill
Hemel Hempstead Liverpool Street Marston Green Oakley
Harlow Mill
Handsworth
Dock Junction Doncaster Belmont East Croydon
Hither Green
Adwick
Acton
Recommendation
Introduce situational RA procedure Make staff aware of goods labelling and location Emphasise requirement for method statements for all jobs Procedure for verifying CAT scan Consistency of Form C acceptance procedure between organisations Formal audit or risk assessments All procedures to be explicit, not implicit Procedure for earth removal Provide opportunity for practice following training Monitor working hours. Provide properly isolated tools Rail shield always used when rail live.
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6.6
Recommendations
Summarising the recommendations from all analyses in this way provides an indication of the human factors interventions that have the potential to have the greatest impact on incidents involving contact with a live conductor. From what was found out about the sample of incidents reviewed, it would seem that safety observation schemes, greater emphasis on supervisory checks, safety communication training and more methodical checks of the planning process are the four interventions that would prove most fruitful in reducing incidents. In addition, it is felt that further analyses of the incident reports to find out how effective they have been in reducing the occurrence of incidents in electrified areas is undertaken. The information presented in the Formal Inquiry Reports lacked in detail and consistency. 6.6.1
Implement Safety Observation Schemes
Safety observation schemes are designed to aid behavioural change by using the principles of providing feedback to reinforce the required behaviours. They revolve around management or employee observations of work areas to identify both safe and unsafe behaviours taking place. The concept then is to provide positive reinforcement for the desired (i.e. safe) behaviour whenever it is observed. The idea is that workers get to know that behaving safely brings recognition and will therefore tend to join in. When an undesired behaviour is observed, rather than punishing the individual, the concept is to sit down with the individual and get them to: (a) (b) (c) (d)
explain what they did explain why they did it describe what the consequences could have been (what’s the worst that could happen) come up with the suggestions for how to do the same job more safely the next time.
The aim should be to get the individual committed to doing the job more safely next time. This process has two objectives – the first is to provide positive feedback on the desired behaviour to reinforce that behaviour. The second is to engage the individual in coming up with a better way of doing that task, to gain their buy-in and commitment to change. We recommend that the concept of Safety Observation Schemes be further researched under Phase 2 of this Project. Benefits In terms of the common causes identified in the previous section, this recommendation would help to identify situations where perceived time pressure is a particular influence, and allow managers and supervisors to re-define their expectations. It would also identify situations where personnel work unsafely due to lack of a formal method statement, risk assessment, or procedure, and allow workers and supervisors the opportunity to define solutions for such cases. It would highlight situations where workers seek the approval of colleagues and managers, allowing the setting of more helpful expectations and examples. Finally, it could provide the opportunity to identify cases where workers are required to implement makeshift adaptations to equipment due to a lack of suitability of the original equipment, and for the workers themselves to highlight any problems. However, this should not be seen as a replacement to sound human factors engineering involvement in the procurement and design of equipment to ensure suitability and usability. The introduction of schemes of this nature will not be easy in today’s disaggregated railway; this however, should not prevent the promotion of what is seen as a valuable tool in improving safety awareness. The use of this concept in many organizations has seen an improvement in safety
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performance. Organisations could be encouraged to do this by inclusions in The Railway Group Safety Plan (RGSP) and through acceptance of Contractor’s Assurance Cases. 6.6.2
Greater Emphasis on Supervisory Checks
Related to the previous recommendation, the evidence emanating from a number of the formal investigation reports seemed to suggest that the frequency of supervisory checks of worksites tended to be very low, and that when they did occur they were not very thorough. Organisations should be required to place a greater emphasis on supervisory checking, which should be used to check that work is being done according to plan and the prescribed procedures, but also helps to raise the level of visibility of the supervisors. Benefits Several of the common causes identified in the previous section would benefit from improved supervisory practices. For example, supervisors would be able to check that suitable method statements and risk assessments were in place and would be in a position to make sure that workers were sufficiently aware of the risks to which they would be exposed. It would also be possible for supervisors to demonstrate commitment to getting the job done safely, and hence help to avoid workers gaining the impression that they are under time pressure. More checks by supervisors would also have the effect of helping to set management expectations in terms of safety and getting the job done. This would help to reduce the number of instances where workers behave unsafely because they think they will get some from of reward for getting the job done, even though it was not a safe way of doing so. 6.6.3
Introduce Safety Communications Training
A number of incidents seemed to involve incomplete or ambiguous information being passed between team members. A great deal of work has been conducted in the recent past to develop guidelines for workers on how best to communicate safety information to make sure that the relevant information is correctly understood. A number of principles to do with giving a good handover are applicable to safety communications in general. These include: Communicating face-to-face whenever possible Using positive statements relating to safety issues (i.e. do not say, “The lever is not in the correct position” because if the middle part of that message were drowned out by noise the recipient might think that the lever was in the correct position. Do say, “The lever is in the wrong position”). Summarise the main points of the communication at the beginning. Where possible, supplement verbal information with written or another form of visual information so that there is redundancy of information to help avoid mistakes. Check that the other person has fully understood, do not take it for granted. Summarise main points at the end of the communication. Person you are communicating with should be actively listening, asking questions and confirming understanding, not just nodding their head. Safety communication training should not be classroom-based, it should provide delegates with the opportunity to practice these skills and go away a better communicator.
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Benefits This would help to tackle the issue of poor risk awareness by helping to ensure that critical information relating to hazards and risks is effectively communicated. However, it would not address the whole issue, and would need to be supplemented with a hazard awareness training and training effectiveness monitoring scheme. This training would need to raise awareness of the conditions under which complacency can impair safety performance, such as ongoing maintenance activities, as this complacency was another of the common causes listed in the previous section. This recommendation would also help to address another common cause, ineffective briefings. 6.6.4
Checking the Planning Process
On a number of occasions, there were failures in the planning process that contributed in some way to the incidents. For example, providing the wrong map of underground services, planning work for red-zone working when there is a T3 possession the following week, having work areas and isolations with different limits, etc. A checking (or auditing) process is required to identify these problems early when they arise, and try to find a safer alternative. There are clear barriers to be overcome – at present, there appears to be a culture in the rail industry that encourages a focus on keeping trains running and avoiding delay. A system that asked for all electrified area working to take place during a T3 possession would not fit within this culture. Some form of step-change is required, similar to the change that was initiated in the offshore industry following the Piper Alpha disaster. The petrochemical industry is living proof that this can be achieved, and the documentation that discusses how to go about ‘changing minds’ is available from the Step Change website (http://step.steelci.org/publications/main_publications_fs.htm). A parallel to the change that is required can be drawn from the implementation of the RIMINI approach for protection of lineside workers. Rather than determine what work can be done under live conditions have a hierarchical approach that looks at the safest possible option first. 6.6.5
Recommended Further Analysis
It would be useful at some later date to perform an analysis of the recommendations generated by the incident reports to find out how effective they have been in reducing the occurrence of incidents in electrified areas. This should involve making contact with the organisations involved in the incidents and finding out how well the recommendations were received, and whether they have been implemented. This would also provide the opportunity to perform a reality-check of the recommendations from this report with these organisations, and obtain impressions of the value added by human factors analysis. The Railway Group Safety Plan (RGSP) already contains a recommendation for Railway Group members to assess safety culture. Reviewing these incidents suggests that to some extent behaviours of workers are being influenced by a ‘can-do’ culture that seems prevalent within the rail industry. This is resulting in workers taking risks in the belief that they will gain acceptance from their colleagues and managers for getting the job done. It would therefore seem that the RGSP recommendation is much needed, and that the assessment of safety culture within the rail industry should be heartily encouraged. An obstacle in the preparation of this report has been the availability and inconsistency of information contained within Formal Inquiry Reports. It is recommended that a review of Standards covering this requirement is undertaken.
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6.7
Predictive Error Analysis
As part of the human factors input to this project, a predictive error analysis was conducted using the task-based risk assessments developed by OLE and DC electrification specialists from Balfour Beatty Rail. The objective of this exercise was to predict the types of human error, which could occur whilst working in AC, or DC electrified areas. The method used to conduct this analysis was a predictive form of the technique used to examine the occurrence of error retrospectively, based upon TRACEr Lite, that was applied to the incidents described in the main body of this report. The technique is driven by a task analysis, which in this case was substituted for the risk assessment referred to above. The process for the assessment is as follows for each task in the task analysis: (i) (ii) (iii) (iv) (v) (vi)
Determine the performance shaping factors associated with that task; Predict the observable errors that might occur (see below for detail); Predict the types of error (perception, memory, decision or action) that might lead to the error as described in (ii); For the chosen error type, determine the most likely error mode (a definition of how the error type manifested itself); Determine the opportunities for recovery from the error described in stages (i) to (iv); Where stage (v) indicates that there are recovery opportunities, determine how likely it is that recovery will be successful;
Once this process was complete, references were made to the severity ratings assigned to tasks in the original risk assessment. In order to tie the assessment results to the analysis of incidents reported earlier, each task was checked against the incident data to determine whether human performance of that task had been a causal or contributory factor in any of the incidents that were analysed. On completion of the analysis, the results were reviewed by electrification specialists from Balfour Beatty Rail over a period of two days to check the feasibility of the errors predicted. An initial meeting was held at The Keil Centre’s Edinburgh office to thoroughly explain the rationale behind the results and ensure that the electrification specialists were comfortable with interpreting the data. Although this form of analysis is based upon the same model as the methodology used for retrospective analysis in the main body of the report, there are some notable differences that the reader needs to be aware of to avoid confusion. Firstly, ‘observable error type’ refers to what indication there would be to a third party that an error had been made (for example, missing a step out of a procedure). This is used in addition to the ‘error type’, which describes what happens in terms of the human information processing system of the person making the error. Secondly, predictive error analysis is also concerned with the opportunities which exist to recover from the error, and how likely successful recovery would be. In order to do this, there needs to be some indication of how the error would manifest itself to a third party (i.e. the observable error type), because it is clearly necessary to be able to detect an error in order to be able to recover from it. Errors, which do not manifest themselves in any way (i.e. they remain inside the head of the person making the error), are clearly more difficult to recover from because detection and recovery
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are in the hands of the person making the error. Errors that do manifest themselves such that others (or electronic systems) stand more of a chance of being recovered. Finally, the term ‘extraneous act’ describes an action that is not required within the task sequence, but which has nevertheless occurred. An extraneous act is not necessarily an incorrect thing to do in itself, but within the context of the task in hand it is inappropriate. An extraneous act can be observed by a bystander, in that an action would be seen that could be recognised as being surplus to requirements for the task. 6.7.1
Results of Predictive Error Analysis
In all, 205 tasks carried out in electrified areas (both AC and DC) were analysed. They comprised tasks involved in inspection of equipment and facilities (i.e. those that do not involve physical contact with energised equipment), those tasks that involve working in close proximity to electrical equipment that may or may not be energised, and those tasks that involve intrusive maintenance of electrical equipment. The initial results of the analysis revealed that the tasks could be divided into three different groups based on the types of error that could occur when performing the tasks. These groups of tasks were examined to identify any common themes in order to allow them to be identified in this report. The following classification system was adopted: 1. Inspection and Servicing – tasks involving only visual inspection of equipment or servicing equipment; 2. Inspection and maintenance in proximity to electrical source – inspections of components of electrified systems (e.g. conductor rail) and maintenance work in the vicinity of the track (e.g. vegetation clearance, boundary maintenance); 3. Maintenance – intrusive maintenance of electrical equipment or working in close proximity to energised electrical equipment. Each of these classifications will now be examined in more detail to provide: an indication of the types of errors predicted in each case an indication of the severity ratings associated with the tasks that make up each class of task whether or not any of the incidents reviewed for the main body of this report involved any of the tasks included within the classification. 6.7.2
Interpreting the Results of the Predictive Error Analysis
In the pages that follow, the results of the predictive analysis are presented in a series of tables accompanied by explanations of the data. This information should be interpreted in the following way: 1.
Review the list of tasks associated with each group. These are located in Appendix E.
2.
Review the list of performance shaping factors for each group. interfere with performance of the tasks in this group.
3.
Review the details of predicted errors. This section begins by providing an indication of the types of error that might be observed (e.g. an extraneous act). For each observable error type predicted, there is then a table, which describes how human information processing might break down and result in the predicted observable error. In each table the error type is listed first (e.g. action error) followed by the error mode – how this error might occur (e.g. selection error). Note that in some cases, there are several ways in which the observable error could come about (e.g. by action, perception or action error). In such
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cases, all feasible ways in which the error could be generated are explained in the table5. The table then goes on to show whether or not the analysis predicts that recovery from the error would be possible, if so the assessed likelihood that recovery from the error would be successful, and a comments field to provide additional explanation. 4.
Following the table there is a list of incidents reviewed for this study, which involved relevant tasks from the risk assessment, and a brief explanation of what happened in each case.
6.7.3
Inspection and Servicing
List of Tasks See list at Appendix E. All tasks in this group received risk rating of “5” or less in the risk assessment (i.e. low risk). Performance Shaping Factors The tasks covered by this classification were most likely to be affected by the following factors: Weather Noise and distraction Alertness / concentration / fatigue
Lighting Familiarity with the task
Details of Predicted Errors The most likely way that an observer would be able to tell that an error had occurred would be observation of an unrequired and incorrect action (i.e. an extraneous act). The following table describes how this could occur: Extraneous Act (unintentionally taking action that is not required) Error Type
Error Mode
Selection error Action (unintended physical action)
Recovery Is Recovery Success Possible? Likelihood Yes
Low – may not have time to intervene
Comments Action error or incorrect positioning of a hand, or tool, results in contact with energized equipment - special consideration should be given to this task, including isolation
None of these tasks was involved in the incidents that were reviewed for this project. 6.7.4
Inspection and Maintenance in Proximity to Electrical Source
List of Tasks See list at Appendix E. The tasks in this group received a risk rating between 10 and 20 in the risk assessment (i.e. they are moderate to high risk).
5 This means that any of the error types could result in the observable error, not that all of them would occur together to produce the observable error.
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Performance Shaping Factors The tasks covered by this classification were most likely to be affected by the following factors: Weather Noise and distraction Alertness / concentration / fatigue
Lighting Familiarity with the task
Details of Predicted Errors As with the inspection and servicing tasks, one of the most likely ways in which errors would manifest themselves would be in extraneous acts (unrequired actions that are also incorrect). In addition to this, errors within this group of tasks are also likely to manifest themselves by operators taking more action than is required to perform the task (e.g. getting too close to live equipment) a type of error expressed as ‘action too much’. The following tables describe how these situations could occur: Extraneous Act (unintentionally taking action that is not required) Error Type Error Mode
Action
Is Recovery Recovery Success Possible? Likelihood
Selection error (unintended Yes physical action)
Low – may not have time to intervene
Comments
Action error or incorrect positioning of a hand, or tool, results in contact with energized equipment - special consideration should be given to this task, including isolation
Action Too Much Error Type Error Mode
Is Recovery Recovery Success Possible? Likelihood
Perception No Perception Yes
Comments
Low to Moderate – more time to intervene Going too close to the energized if a worker is seen to equipment because of failure to be getting too close to perceive proximity to it energized equipment
Two of the incidents reviewed for this project were related to one of the tasks from this group – manual vegetation clearance. Adwick in August 2000 involved vegetation clearance but involved a violation by one of the workers rather than a human error. The Leighton Buzzard incident of June 1985 also involved vegetation clearance, but there was insufficient information in the investigation report to determine the human factors cause.
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6.7.5
Maintenance
List of Tasks See list at Appendix E. All tasks in this group were rated above 20 in the risk assessment (i.e. high risk). Performance Shaping Factors This was by far the largest group of tasks identified, covering a range of tasks involving maintenance work on or around electrical equipment. This includes intrusive maintenance of electrical equipment or maintenance in close proximity to energised electrical equipment. Due to the range of tasks involved the factors likely to affect the performance of those carrying out the tasks is extensive, as shown in the following list: Time pressure;
Non-standard activities;
Procedure availability/access/location;
Weather;
Lighting;
Temperature;
Familiarity with task;
Level of experience;
Recency of training;
Training quality;
Competence testing;
Mentoring quality;
Alertness/concentration/fatigue;
Complacency;
Team co-ordination quality;
Handover/take-over;
Team maturity;
Supervision;
Staff availability;
Details of Predicted Errors Many of the tasks in this group were more complex than in the previous two groups, and therefore presented more opportunities for error. The following list describes the ways in which errors could manifest themselves in this type of task: Action Too Much – doing more than is required, e.g. getting too close to an energised electrical source; Extraneous Act – action that is not required and is incorrect, e.g. unintentionally touching a wrench to the energised conductor rail. Action too Early – action that occurs at the wrong time, e.g. driving a vehicle off before all of the workers are on board; Right Action on Wrong Object – the choice of action is correct but the selection of object is incorrect, e.g. cleaning one of several section insulators, but selecting a live one by mistake; Action in Wrong Order – an action is conducted at the wrong point in a sequence, e.g. unintentionally starting work before testing has been completed; Omission – an action that should have been taken is missed out, e.g. failing to conduct live line testing prior to commencing work. The analysis suggested that there were a number of types of error, which could lead to the occurrence of these observable errors. The following tables describe the predicted errors in more detail, including the likelihood of recovery.
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Action Too Much Error Type Error Mode
No Perception Perception
Is Recovery Possible?
Recovery Success Likelihood
Comments
Yes
Low to Moderate – more time to intervene if a worker is seen to be getting too close to energized equipment
Going too close to the energized equipment because of failure to perceive proximity to it
Extraneous Act (unintentionally taking action that is not required) Error Type Error Mode
Action
Selection error (unintended physical action)
Is Recovery Possible?
Recovery Success Likelihood
Comments
Yes
Low – may not have time to intervene
Action error or incorrect positioning of a hand, or tool, results in contact with energized equipment - special consideration should be given to this task, including isolation
Is Recovery Possible?
Recovery Success Likelihood
Comments
Action Too Early Error Type Error Mode
Perception Misperception Yes
Memory
Forget information
Decision
Misjudgement Yes
Yes
E.g. Accessing equipment too Low – could be difficult if early because equipment the misperceived status information has been information is credible misperceived Accessing equipment too early because the checking Low – difficult for others procedure or other to detect a memory failure information relating to equipment status is forgotten Low – difficult to recover Making a judgment about the is basis of judgment is safety of working around live credible, also difficult for equipment, which is in some co-workers to detect a way lacking decision failure.
Right Action on Wrong Object Error Type Error Mode
Is Recovery Possible?
Recovery Success Likelihood
Perception Misperception Yes
Low to moderate– relies on further checks by individual or detection of mistake by co-workers
Memory
Low to moderate– relies
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Misrecall
Yes
Issue 1
Comments
Action taken on a live piece of equipment instead of the intended de-energised or nonelectrified equipment due to perceptual confusion between pieces of equipment Action taken on a live piece
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on further checks by individual or detection of mistake by co-workers
of equipment instead of the intended de-energised or nonelectrified equipment due to misrecall of the equipment reference number, location, isolation limits, etc. Action taken on a live piece of equipment instead of the intended de-energised or nonelectrified equipment due to action error resulting in inappropriate selection of equipment
Yes
Low – difficult to intervene in time to prevent harm
Error Type Error Mode
Is Recovery Possible?
Recovery Success Likelihood
Comments
Memory
Yes
Low
Misrecall of work procedure leads to a step in a procedure being taken out of sequence
Is Recovery Possible?
Recovery Success Likelihood
Comments
Action
Selection error
Action in Wrong Order
Misrecall
Omission Error Type Error Mode
Memory
Late/missing Yes action
Forget Information Misrecall
Decision
Failure to confirm isolation in place (e.g. live line testing) or check equipment status prior Low to Moderate – reliant to commencing work. Could on co-worker to spot the be due to memory failure omission before harm or stemming from a late or last minute realization by missing action, information the worker being forgotten (e.g. forgetting procedure) or misrecall of information
Yes
As above
As above
Yes
As above
Poor decision Yes / plan
As above
As above Failure to check of equipment status, or confirm isolation caused by a poor decision or plan, which does not include provision for standard checks, leading to work commencing with equipment energized
Twelve of the incidents reviewed for this project involved tasks that fall into this group. Of these, seven were classified as errors and the remaining five were violations. Further details of these incidents are provided below:
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At East Croydon in September 2002, a worker was electrocuted whilst replacing cable tubing near the rails. The analysis of this incident indicated that this was a violation rather than an error. At Oakley in August 2003, a lookout was electrocuted when he joined in with the replacement of insulator pots. This was found to be a violation rather than an error. At West Croydon in October 2001, two workers were injured whilst maintaining a rail flange lubricator when an uninsulated spanner contacted the energised conductor rail. A human error analysis was performed which suggested that this was an action error (specifically a selection error because it was a physical action) and that this was most likely due to human variability in physical performance (i.e. the same person does not always perform to the same level of precision, their performance will naturally vary). This is in line with the predicted action (selection) error leading to an observed extraneous act. The most effective solutions to prevent such errors of action involve removing the hazard or physically separating the worker from the hazard. In the analysis of this incident, the recommendations covered working under T3 conditions, ensuring properly insulated tools are used, and the use of rail shields. At Doncaster Belmont in December 2001, a worker died when he climbed on top of a wagon, presumably to check its contents. The worker was alone at the time and so the circumstances behind the accident are unclear. However, a human error analysis suggested that the most likely course of events were that the worker made a poor decision regarding climbing on top of the wagon due to a lack of knowledge. The knowledge that was most likely missing was that he could check the contents from the label (or perhaps where the label was located), and there may have been a lack of knowledge regarding the dangers of overhead lines. Recommendations covered the provision of training on the hazards associated with AC equipment, the use of situational risk assessments, and familiarity with goods wagon labelling. At Harlow Mill on the 5th May 2002, a worker received an electric shock when redistributing the load on top of a wagon. This was an error on behalf of the Engineering Supervisor, who had made a poor decision based on a faulty mindset. Recommendations covered effective communication training, guidance on high-risk handovers, checking procedures and audits of COSS briefings. At Tollerton in May 2001, several workers received electric shocks during the unloading of track by a crane that fouled the overhead line during a renewals project. Investigation of the incident suggested that this was a violation rather than an error. At Hemel Hempstead in August 2001, a worker received an electric shock when cleaning a section insulator. Two errors were identified, one on behalf of the worker and one on behalf of the person giving the briefing. One was an action error (unclear information on location of live equipment); the other was a perception error where information was misperceived due to confusion. Recommendations covered the conduct of line testing in complex areas and provision of safety communications training. At Marston Green in July 2003, workers received electric shocks during preparation for work on the OLE. Analysis of the incident revealed that this involved a violation rather than an error. At Ranskill in October 1998, a worker was killed when he removed the earth end of a long earth before the line end. Analysis revealed that this was a perception error stemming from a misperception that a colleague had removed the line end. Recommendations covered a oneman procedure for removing earths, effective communications training, refresher training and opportunities to develop skills, and auditing of records of working hours.
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At Liverpool Street in November 1999, a worker was injured when he made contact with the OLE whilst climbing some scaffolding. Analysis suggested that this was a perception error (misperception of correct location by the contractor) caused by confusion between different locations on the station that looked similar. Recommendations covered coinciding worksite and isolation limits, and regular audits by the site safety authority. An incident at Dock Junction in February 2002 involved workers trying to dismantle a scaffold under OLE following a shortening of the possession which meant that there was not time to complete the job safely. This was classified as a violation rather than an error. At Handsworth in March 2002, two workers were burned when they ruptured a buried 132Kv oil-filled HV cable. The analysis suggested that this was due to an error of perception (failure to perceive information), caused by their expectations regarding what was buried at the worksite. Recommendations included planning documentation with enhanced detail and procedures for encounters with buried objects. 6.7.6
Summary
The predictive analysis of human error conducted to supplement the risk assessment of tasks conducted in electrified areas suggested that the predominant types of error that would be encountered would be perception, action and memory errors. Most tasks do not provide the opportunity for decision-making errors, although these were also predicted. It was felt that decision-making errors would be more likely in planning and management tasks than in manual tasks. The review of previous incidents reported in the main body of this document suggested that the most common form of error was the perception error, which occurred four times in those incidents reviewed. There were also two action errors and two decision-making errors. None of the incidents reviewed included memory errors. The incidents that were reviewed were, largely, associated with tasks that have been classified under the higher risk classification categories in the risk analysis (i.e. those that have a rating of 20 or 25 on a 5 x 5 scale). A number of incidents have involved error types that have also been predicted for other tasks that so far, and to the best of our knowledge, have not been involved in incidents. It is therefore important that means of reducing the likelihood that such errors will occur in future, or if they do their impact can be lessened, should be afforded a high level of importance. In the main body of this report, the analysis of the sample of electrification incidents resulted in a series of recommendations directed towards preventing or mitigating similar events in the future. The results of this predictive analysis can be used to generate more generic recommendations that can be applied to a greater range of tasks. Based upon the output from the predictive analysis, the following section documents some generic recommendations, which should be considered for reducing the likelihood and impact of errors for all tasks that receive higher risk classifications in the first instance. It is not recommended that such error-reduction measures only be applied to the higher-risk tasks, although these should receive priority attention. Other tasks should be given similar attention once the higher-risk tasks have been addressed. 6.7.7
Generic Recommendations
These recommendations are presented grouped by the type of error (perception, memory, decision or action) that they are designed to address. These recommendations are generic; to apply them they should be interpreted in the context of the specific task (or tasks) to which they are to be applied. They are intended to provide a starting point from which to develop a specific recommendation to fit a particular situation.
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Perception Error Recommendations 1. Introduce checking procedures to be followed by people operating in the more risky conditions to trap errors prior to incidents. 2. Raise awareness of conditions under which tunnel vision (focussing on one piece of information at the expense of others) can cause difficulties (e.g. emergency conditions and other high-stress situations). 3. Train and educate personnel to develop situational awareness skills to reduce the likelihood that they will distract others during performance of critical tasks and increase the likelihood that errors caused through distraction will be identified early. 4. Raise awareness of the influence of distraction and preoccupation on error rates and encourage personnel to consider these as part of a personal risk assessment prior to conducting work. Personnel should feel able to raise preoccupations and distractions that they feel could affect safety through programmes such as “Time Out for Safety”. 5. Provide means of clearly distinguishing de-energised equipment from energised equipment (e.g. marker boards, brightly coloured isolation permits, etc).
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Memory Error Recommendations 1. Design training to include a period of practice prior to returning to the job. 2. Raise awareness throughout the workforce of the safety impact of lack of learning and encourage the reporting of instances where they feel risks exist (e.g. through existing open reporting systems, Time Out for Safety, etc.). 3. Provide aides mémoire for critical tasks to reduce memory load. 4. Provide regular emergency training to reduce the probability of memory failure. 5. Ensure that multiple team members have the information required for critical tasks to introduce redundancy. 6. Review procedures regularly with members of the workforce to reduce ambiguity and complexity and ensure that they are fit for purpose, effective and easy to use and remember. Decision Error Recommendations 1. Provide training in decision making in order to increase skills in integrating several information sources, considering potential side effects of actions, checking the validity of plans as the situation unfolds. 2. Introduce procedural checks by other personnel to detect errors in time to correct them. 3. For critical actions, use multiple personnel in the decision-making process to increase the probability that decision-making failures will be identified early. 4. Ensure that newly trained personnel receive mentoring or supervision for a period of time to ensure that training has been successful 5. Introduce a formal training evaluation procedure to identify shortcomings in existing training interventions. 6. Ensure that all personnel receive the training required to enable them to fulfil their duties safely and reliably. 7. Introduce situational awareness training to help ensure that all team members are aware of all stages of the decision-making process and are able to intervene should there be a problem. Action Error Recommendations 1. Design the working environment to account for variation in body size and inaccuracy of positioning (e.g. make steps wide enough to accommodate 5th percentile female shoe size up to 95th percentile male shoe size). 2. Ensure that all personnel are provided with adequate practical skills training to meet operational requirements. 3. Ensure that training is in place to overcome potential confusion associated with habits from previous jobs or changes to equipment. 4. Raise awareness of conditions under which thoughts and habits can intrude and encourage team members to be more vigilant under such conditions.
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7 7.1
Task Identification and Risk Analysis Methodology
This element of the research has included the identification of tasks that are undertaken by maintenance and renewal teams on the electrified railway. The scope of tasks examined included Permanent Way; Signals; Telecommunications; Contact Systems (both AC and DC); Power Distribution and Off Track activities, which include vegetation clearance and drain cleaning. In excess of 600 tasks performed on the operational railway were identified and risk assessed. The breakdown of tasks against each function is shown in the table below: Function Permanent Way Signalling Telecommunications 750 V DC Conductor Rail 25 kV AC Overhead Line Power Distribution Off Track Activities Total
No. of Tasks Identified Overhead Line DC Conductor Rail 62 62 88 83 43 47 N/A 36 49 N/A 23 24 51 61 316 313
Having identified the various tasks, a panel of experienced personnel from within the Balfour Beatty Rail Group of Companies was formed. The panel reviewed the risk associated with undertaking each task and ranked it in terms of likelihood and severity assuming that only base line controls were in place. The base line controls included basic competence e.g. PTS and any specific competence requirement required for the task such as Level A, B or C Competency for working on or near live electrical equipment. RT/E/S/21070, RT/E/P/24001 and RT/E/C/27018 refer. Risk assessments were carried out in accordance with a risk rating approach using a 5 x 5 matrix. Degree of risk (rating) = likelihood x severity. Numerical Value 1 2 3 4 5
Likelihood Improbable Remote Occasional Probable Frequent
Definition Extremely unlikely to occur Unlikely to occur Likely to occur once Likely to occur more than once Extremely likely to occur
Numerical Value 1
Severity Negligible
2
Minor
3 4 5
Noticeable Major Fatal
Definition Little risk of injury or disease Minor injury that may result in less then one shift loss time Lost time injury of more then one shift Accident or Incident reportable under RIDDOR Loss of life
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The above values are then multiplied together to give a risk ranking as follows: Likelihood 1 1 2 3 4 5
1 2 3 4 5
Risk Rating
Class
1 to 3
Negligible
4 to 5
Low
6 to 9
Medium
10 to 14
High
15 to 25
Unacceptable
2 2 4 6 8 10
Severity 3 3 6 9 12 15
4 4 8 12 16 20
5 5 10 15 20 25
Control Action Ensure identified controls are in place. Monitor work to ensure no increase in risk Ensure identified controls are in place. Monitor work to ensure no increase in risk Ensure controls are in place. Monitor and review work methods to further reduce risk Action required to control risk. Review work methods to reduce risk. Monitor situation Action required to modify work methods and introduce controls to reduce risk rating
Having followed the format detailed above across the range of tasks identified in both an overhead line and DC electrified railway scenario, 202 of the tasks assessed fell into the red risk category with only base line controls applied. Shown in the chart at 7.2 is an example of the process adopted for a number of tasks undertaken in the category of Permanent Way Engineering. As can be seen for these tasks, only two falls into the red risk category and requires additional control measures to be applied to bring the risk down to a tolerable level. Additional control measures for these activities could include additional training, using surveying equipment in OLE areas that is non-conductive, physical stops on the telescopic poles to restrict their height or in the extreme, only undertaking this activity when the overhead line has been isolated and earthed. In view of the number of tasks identified, it was decided to concentrate on those, which fell into the red risk category. The charts shown at Appendices F1 to F10 inclusive detail the tasks, which came out as red risks with only basic controls being applied. The column on the extreme right of the charts highlights areas where additional control measures could be applied to bring the risk down to a tolerable level. This may mean in some instances only doing those tasks under isolated and earthed conditions. The degree and extent of the additional control measures should reduce the residual risk down to one that does not put employees at undue risk.
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7.2
Example of Task Identification and Risk Assessment Process
Task List and Risk Assessment for Permanent Way Engineering in OLE Area Proximity to OLE Task
Description
Key Electrical Risk
>2.75 600mm 300 < mm 300mm
Basic Control Measures
Possible Mitigations
L
S
Total
4
5
20
Isolation Required
Maintenance of Rails
Intrusive maintenance
Maintenance of Fastenings
Intrusive maintenance
Staff or equipment coming into contact with live con rail Ditto
4
5
20
Isolation Required
Maintenance of Insulators
Intrusive maintenance
Ditto
4
5
20
Isolation Required
Maintenance of Cables
Intrusive maintenance
Ditto
4
5
20
Isolation Required
Maintenance of Continuity Bonds Maintenance of Conductor Rail Equipment Protection Boarding Removal and replacement of cables and tamper proof tubing from underneath rails
Intrusive maintenance
Ditto
4
5
20
Isolation Required
Intrusive maintenance
Ditto
4
5
20
Isolation Required
Intrusive maintenance
Ditto
4
5
20
Isolation Required
Ditto
4
5
20
Isolation Required
Ditto
4
5
20
Isolation Required
Ditto
4
5
20
Ditto
4
5
20
Isolation Required Safe System of Work required. development of new non contact gauge
Ditto
4
5
20
Ditto
Painting Ramp Ends
Intrusive maintenance Profile gauging using insulated gauge Spatial gauging using insulated gauge Intrusive maintenance
Ditto
4
5
20
Isolation Required
Changing Traction negative bonds
Intrusive maintenance
Ditto
4
5
20
Safe System of Work required
Changing Insulator Pots
Intrusive maintenance
Ditto
4
5
20
Isolation Required
Applying Conductor Rail Wraps
Intrusive maintenance
Ditto
4
5
20
Isolation Required
Replacing Conductor Rail Cutting and Welding Conductor Rail Fitting Attachments to Conductor Rail Tapping of pre drilled holes in conductor rail to facilitate the connection of fittings
Intrusive maintenance
Ditto
4
5
20
Isolation Required
Intrusive maintenance
Ditto
4
5
20
Isolation Required
Intrusive maintenance
Ditto
4
5
20
Isolation Required
Intrusive maintenance
Ditto
4
5
20
Isolation Required
Intrusive maintenance
Ditto
4
5
20
Isolation Required
Fitting of terminations to cables Drilling Conductor Rail Drilling of running rail Profile Gauging of Conductor Rail Spatial Gauging of Conductor Rail
Hookswitch Changing
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Crimping cables using hydraulic crimping tool Intrusive maintenance
Issue 1.
Potential for
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Task Fitting and Removal of Third Rail Short Circuiting Device Tripping of Circuit Breaker using short circuiting bar Install glass fibre shrouding under conductor rail
Description
Key Electrical Risk
Proximity to Conductor Rail >300 < mm 300mm
Basic Control Measures L
S
Total
Possible Mitigations
Isolation Procedures
Ditto
4
5
20
Undertake task in accordance with GO/RT 3091
Isolation Procedures
Ditto
4
5
20
Undertake task in accordance with GO/RT 3091
Intrusive maintenance
Ditto
Fitting Arc Control Shield
Intrusive maintenance
Ditto
4
5
20
Isolation Required
Tunnel Patrol
Foot Patrol and Visual Inspection of the P Way
Ditto
3
5
15
All staff undertaking these tasks have been trained and certificated to PTS requirements
Intrusive maintenance
Ditto
4
5
20
Safe System of Work required
Intrusive maintenance
Ditto
4
5
20
Safe System of Work required
Maintenance of Switches and Isolators Maintenance of Cathodic Protection Systems
Isolation Required
Note: The possible mitigations are for consideration only. Where tasks indicate an unacceptable risk then appropriate control measures should be developed to bring the residual risk down to a tolerable level.
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Appendix F10
Task List and Risk Assessment for Off Track Activities in DC Conductor Rail Area Showing Red Risks
Task
Description
Vegetation clearance using flail Cutting back of lineside vegetation mower mounted on "on track" using "on track" machine machine Vegetation clearance using manual Cutting back of lineside vegetation methods using hand tools Survey undertaken by staff from Vegetation Survey Cess or foot patrol from track Drainage clearance (manual Staff using long rods rodding) Drainage clearance (high pressure High pressure water jet machine water jetting)
Key Electrical Risk
Basic Control Measures
Proximity to Conductor Rail
>300 < L mm 300mm
S
Total
Staff or equipment coming into contact with live con rail
3
5
15
On/Off tracking needs to be considered
Ditto
3
5
15
Safe System of Work required to ensure activity is kept more than 300mm away from Con Rail
Staff or equipment coming into contact with live con rail
3
5
15
Activity is away from live con rail
Ditto
4
5
20
Possible Isolation required
Ditto
4
5
20
Possible Isolation required
Ditch clearance
Staff Working at Rail Level
Ditto
3
5
15
Culvert clearance (all diameters)
Staff Working at Rail Level
Ditto
3
5
15
Catchpit maintenance
Staff Working at Rail Level
Ditto
3
5
15
Drainage maintenance
Staff Working at Rail Level
Ditto
3
5
15
Ditch maintenance
Staff Working at Rail Level
Ditto
3
5
15
Culvert maintenance (
