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Modeling parking lots and zones

In the dynamic assignment the start and destination points of the vehicles must be located in parking lots. One parking lot is always assigned to one zone only. Trips originating from this zone or ending in this zone can begin or end at this parking lot. A zone can have more than one parking lot. You define the originating traffic with a distribution to the desired parking lots. The distribution of destination traffic across multiple parking lots of a zone is computed by a parking lot choice model (Defining the destination parking lot selection). As the start and destination points of vehicles lie on parking lots that are allocated to zones, Vissim distinguishes between origin and destination zones. You can show the relation between an origin zone and a destination zone in the OD pairs list (Attributes of OD pairs). Result attributes that are created between origin and destination zones during a simulation run can be entered in the evaluation OD pairs and displayed in the list OD Pair Results (Displaying OD pair data in lists).

If you want vehicles to drive from a parking lot of a certain district to another parking lot of the same district and Vissim finds a path, the simulation includes the district’s entire traffic for this OD relation. If there is no other parking lot the same district, vehicles do not drive back to their start parking lot.

Traffic starting at a parking lot behaves similarly to the traffic generated by vehicle inputs (Modeling vehicle inputs for private transportation). However, the vehicle composition is not specified at the parking lot, but arises from the vehicle compositions of the source-destination matrices that produce traffic in this parking lot.

The desired vehicles speeds are not taken from the distribution specified with the vehicle composition in the matrix, but from the default desired speed distributions which you choose from the parking lot attributes. In addition, you can assign individual vehicle classes a defined desired speed distribution.

With desired speeds at parking lots you can take into account different speed limits in the parking lot area.

Vissim uses vehicles in the network from simulation start. This allows you to assign a vehicle a path via the COM interface when it leaves its origin parking lot.

The number of vehicles inserted into an origin parking lot corresponds to the value listed in the origin-destination matrix. The origin parking lot is chosen based on whether the Use volume (old) attribute on the Choice tab of the parameters for dynamic assignment is selected:

• If the Use volume (old) attribute is deselected, the origin parking space is chosen based on the Rel. volume attribute of the parking lots in the zone where the vehicle starts.
• If the Use volume (old) attribute is selected, the origin parking lot is chosen based on the volume specified in the *.weg path file. The Rel. volume attribute is then not taken into account. The time intervals of path volumes may differ from the time window defined for the origin-destination matrix in the From-time and To-time attributes. This is why path volumes adopted from the *.weg path file are scaled using the part of the time interval that lies within the valid period of the origin-destination matrix. These scaled path volumes are added up for all time intervals and paths leading to the destination zone of the OD pair. This equals the relative volume of a parking lot. The total of relative volumes for all parking lots of the origin zone of an OD pair is the normalization factor required to calculate the probability of selection of a parking lot. If the total of probabilities equals 0, then no parking lot is selected and no vehicles are used in this zone.

The relative volume for a parking space is 0 in the following cases:

• When there is no path between the parking lot and a parking lot in the destination zone
• When the capacity of the parking lot is exhausted

When the origin parking lot is of the type Real parking spaces and the capacity of the parking lot has been reached, the vehicle is not be added to the network.