Vissim Training - 12. Dynamic Routes

PTV VISSIM Training Dynamic Routes

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BUDI YULIANTO

DYNAMIC ASSIGNMENT 

Principle of Microscopic Dynamic Assignment

no assessments no paths

1st Simulation

costs from (k-1)th simulation all previously found paths

nd Simulation kth 2 Simulation

T

k,

distance as assessment all vehicles on shortest path

first set of costs first set of paths

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new set of costs some additional paths

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DYNAMIC ASSIGNMENT

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Parking Lot Parking Lots: the point where the vehicle actually appear or leave the road network. 

Parking Lot types 

Zone connector (no slow down or capacity)

 Abstract parking lot (vehicles slow down, capacity inc)

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Real parking lot (stop upon entry)

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Max. One parking lot between two nodes

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Place parking lots between two nodes Wrong:

Correct:

Wrong:

Correct:

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Nodes and Edges Nodes: parts of the network where paths could diverge (as a junction). Edges: the basic building blokcs of the routes, i.e. a route is sequence of edges (as a link). Nodes 

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Network abstraction: 

nodes (black polygons)

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edges (link sequence between two nodes or within a node) 

edges inside nodes

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Edges between nodes

Each decision and merging point of a possible route should be placed within a node www.ptvgroup.com

Edges

Wrong:

Correct:

Wrong:

Correct :

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OD Matices 

Trip Matrix (FMA file) : create using VISUM, Text Editor  Time Interval Same as the Simulation Time Factor  To scale the matrix globally

To zone

Zone Number  Numbers of all zones that are used in the matrix

  e   n   o   z   m   o   r    F

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Modelling Elements 

Connector closures: Prevent certain vehicle classes to use certain parts of the network

 Additional links and connectors to place parking lots

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Nodes: abstract definition of junctions

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Parking lots: for all origins and destinations of traffic (also zone connectors)

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Dynamic Assignment process parameters

 Additional evaluations (e.g. paths, convergence)

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Dynamic Assignment Parameters 

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Multiple matrices can be defined such as multiple time intervals, different traffic composition, etc Cost and Path files store necessary Dynamic  Assignment information for next iteration

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Check Edges Box  – this function checks whether the network has changed since you created the input path or cost file. If network has changed it will give you a message telling you so.

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One of the most common causes of error in dynamic assignment is when you use an existing cost or path file with a network that has been changed since the cost/path file was created.

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You should always have this box selected otherwise, always ensure that the existing path file has been deleted or renamed.

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Dynamic Assignment Parameters

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Scale total volume to avoid Initial congestion

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Evaluation interval defines how costs and paths are evaluated 

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 Activate to write files during Dynamic  Assignment process Deactivate when Dynamic Assignment process is complete

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Store costs: if checked, VISSIM will writes a new cost file

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Search new paths: if checked VISSIM calculates new shortest paths through the network

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Store paths: if checked VISSIM stores new paths and their volumes in the path file

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Dynamic Assignment Parameters

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Kirchhoff exponent defines polarisation of path distribution

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Logit function defines parking lot choice model

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Correction of overlapping paths affects vehicle distribution on paths which are partially identical

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 Avoid long detour, paths with long detours will not be used for vehicle distribution,

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Definition of convergence criteria of Dynamic  Assignment 

Travel time on paths: computes the change of TT on every paths compared to its TT in the previous run. If change for all paths < the user-defines factor, convergence for this criterion is detected.

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Travel time of edges

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Volume on edges www.ptvgroup.com

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Dynamic Assignment Parameters 

Correction of overlapping paths Example: 3 paths with identical length, 2 of them partial identical (overlapping) Without correction 1/3

2/3

A

< 2/3

1/3

B

1/3

2/3

A

With correction

1/3 1/3

1/3

~1/3

B

A

B

> 1/3

> 1/2

Vehicle distribution identical regardless of length of overlapping section www.ptvgroup.com

A

~1/3

~1/4 ~1/4

< 1/2

B

Vehicle distribution depends on length of overlapping section

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Urban Road Network Model

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Convergence of Path Serach 400 350

  s 300    h    t 250   a   p 200   w   e 150   n 100 50 0 1

11

21

31

41

51

61

71

51

61

71

81

Iteration

40000

75 Zones

35000 30000    d   n   u   o    f   s    h    t   a   p

25000 20000 15000 10000 5000 0 1

11

21

31

41

81

Iteration

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Road Closure 

Connectors (turning movements can be closed to specific vehicle classes

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Convergence Evaluation 

Convergence output file to check if the Dynamic Assignment process is complete or not

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PRACTICE CODING DYNAMIC ASSIGNMENT

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