Using distributions

There are various use cases for stochastic distributions in Vissim, for example the desired speed of vehicles on certain network objects or the weight and power of HGVs.

Defining a distribution

You can define empirical distribution functions for the distributions in the two lists below (Defining the empirical distribution). When defining the distribution, you enter the values for lower bound and upper bound. Between the lower bound and the upper bound, in the curve, you can insert intermediate points, drag them with the mouse to the desired value and thus define the curve of the distribution. In general, two nodes are sufficient to achieve more or less an S-shaped distribution, and thus a concentration around the mean value.

• Desired speed (Attributes of desired speed distributions)
• Power (Attributes of power distributions)
• Weight (Attributes of weight distributions)
• Location (Attributes of location distributions)
• Distance (Attributes of distance distributions)

You can also define distribution functions based on a normal distribution for the following distributions (Defining a normal distribution). When defining the distribution, you enter the values for standard deviation and mean:

• Time (Attributes of time distributions)
• Occupancy (Attributes of occupancy distributions)
• Free distribution (Attributes of free distributions)

The values of the distributions are displayed depending on the network settings for units (Selecting network settings for units).

You can also define the following distributions:

• Define color distributions for visualizing vehicles and pedestrians of a given type (Using color distributions), (Defining color distributions)
• You can use a 2D/3D model distribution instead of a single model for vehicles or pedestrians of a given type (Using 2D/3D model distributions), (Defining 2D/3D model distributions for 2D/3D models).
• Emission class distributions for the relative share that each emission class of an emission class distribution has (Using emission class distributions), (Defining emission class distributions)

Deleting a distribution

You can select and delete distributions in the respective list of distributions (List toolbar). Network objects assigned to these distributions are then also deleted. When you delete a 2D/3D model distribution, the vehicles types assigned to it are deleted as well! As a result, associated vehicle categories or vehicle classes may contain fewer or no vehicle types, Vissim adjusts vehicle inputs by deleting relative volumes.

• ►  Before deleting a distribution, assign the network objects that you do not wanted deleted to a different distribution.