Time-varying attributes

The procedures SBA (Simulation-based dynamic assignment (SBA)), DUE (Dynamic User Equilibrium (DUE)) and dynamic stochastic assignment (Dynamic stochastic assignment) allow you to model time-dependent transport supply. In Visum, time-varying attributes are used for this purpose. Time-varying attributes only affect these assignment procedures.

Otherwise time-varying attributes override the valid value of an attribute with a deviating value for a certain amount of time. They can thus model, for example the impact of tidal flow lane allocation or transient road works.

Time-dependent attributes can be assigned to the following network objects.

  • Links
  • Turns
  • Main turns
  • Node
  • Main nodes

For these network objects, only specific attributes can be time-varying, and the deviating value of the attributes is not relevant to all procedures. The Table 27 gives an overview of which attributes can be time-varying in which assignment procedures.

Table 27: Time-varying attributes and their allocation to assignment procedures

Network object

Time-varying attribute

SBA

Dynamic Stochastic Assignment

DUE

Links

 

 

 

 

 

 

Out capacity PrT

 

 

X

Capacity PrT

 

X

X

Toll-PrTSys

X

 

X

v0 PrT

X

X

X

TSysSet

X*

X

 

AddValue 1-3

X

 

 

AddValue-TSys

X

 

 

Turns

 

 

 

 

Capacity PrT

 

X

X

ICA final capacity

 

 

 

t0 PrT

 

X

 

TSysSet

X*

X

 

AddValue 1-3

X

 

 

Main turns

 

 

 

Capacity PrT

 

X

X

t0 PrT

 

X

 

TSysSet

X*

X

 

AddValue 1-3

X

 

 

Nodes

 

 

Capacity PrT

 

X

 

t0 PrT

 

X

 

AddValue 1-3

 

 

 

Main nodes

 

 

Capacity PrT

 

X

 

t0 PrT

 

X

 

AddValue 1-3

 

 

 

* = With time-varying attributes, links may only be closed, but not opened.

The example in Table 28 illustrates the effect of time-varying attributes using the example of the Dynamic Stochastic assignment. The upper image shows the volumes and the capacity PrT on the links in time period from 5 am to 7 am. The lower image shows the volumes and the capacity PrT in the time period from 7 am to 9 am (a constant time series has been used here to simplify the comparison of both conditions, so that the traffic supply is the same in both of the time intervals).

Table 28: Impact of time-varying attributes in the Dynamic Stochastic assignment

The links 11 - 41 and 41 - 40 are charged with the full capacity of 800.

With the aid of a time-varying attribute for the capacity PrT on the two links (11-41 and 41-40), both links are charged with a reduced capacity of 100. Therefore, the volumes of the links are lower.