Calculating EVA trip generation

Similarly to the trip generation of the Standard 4-step model (Calculating trip generation), the EVA trip generation calculates the production and attraction of each zone per demand stratum. Additionally, the model determines the home trips of each zone per demand stratum. On this basis, the productions and attractions are standardized. For demand strata of OD type 1, the productions are equal to the home trips, for those of OD type 2, the attractions are equal to the home trips. Those cases do not require separate parameters for the calculation of the productions and attractions (Fundamentals: EVA trip generation).

1. On the toolbar, click the Open 'Procedure sequence' window button.

The Procedure sequence window opens.

2. To the procedure sequence, at the position of your choice, add the procedure EVA trip generation of the Demand model category (Setting up and starting the procedure sequence).

3. In the row of the newly inserted procedure, in the Reference object(s) column, click the button.

The Demand strata selection window opens.

4. In the Select demand model list, click the demand model the demand strata belong to.

5. In the Demand stratum selection list, select the demand strata you would like to calculate the EVA Trip distribution for.

Tip: To select multiple demand strata, hold down the Ctrl key while clicking the desired entries one by one.

6. Confirm with OK.

The demand strata selected are listed in the Reference object(s) column.

7. Make sure the added procedure is marked. Then, in the Operations section, click the Edit button.

The Parameters: EVA trip generation window opens.

8. Make the desired changes.

Element	Description
For active zones only	If this option has been selected, EVA trip generation is performed for active zones only (Using filters to set network objects active or passive and Setting network objects active/passive via the spatial selection).
Set all result attribute values to 0 prior to calculation	If this option has been selected, all output attribute values are set to zero prior to the calculation.
Use subspace balancing	If the option is selected, the attribute set here will be used to group zones. Zones with the same attribute value form a group. The procedure then carries out the generation separately for the zone groups. Thus, the source and destination potentials are balanced only within the zone groups. Attribute for the definition of the subspaces Select the numeric attribute on the basis of which you want to group the zones.
Execute balancing	If this option has been selected, balancing is performed at the end of the EVA trip generation run (Fundamentals: EVA trip generation). Notes The option is only available if the following criteria are met: You have selected balancing for exactly one demand stratum (of OD type 3). You define the demand stratum for which to compute balancing on the Constraints tab under Demand > Demand models (Defining constraints). Hard constraints are defined for all demand strata on both sides, origin and destination. All modes of the demand model are interchangeable. However, balancing can be calculated at the end of the EVA trip distribution and mode choice operation (Calculating EVA trip distribution and mode choice).
Key	Unique value generated by Visum for each combination of Demand stratum, Kind of trip and Person group / Structural property.
Demand stratum	List of all demand strata selected for the procedure. One row per key.
Type (origin destination type)	Display of the direction of the activity pair with regard to the home activity (Fundamentals: EVA trip generation), (Properties and options of activities)
Kind of trip	Kind of trip of the respective combination of demand stratum and person group / structural property
Person group / Structural property	Person group / Structural property of the demand stratum
Rate constant	If this option has been checked, the mobility rate of the person group is constant for the demand stratum, i.e. it is the same for all zones. If the option is not selected, a specific value (from zone attribute) is regarded for each zone.
Rate	If you select the Rate constant option for a person group, you can enter a value ≥ 0 for the specific demand of this group.
SA factor constant	If this option is selected, the value of the intrazonal demand is constant for the attraction rate, i.e. it is the same for all zones. If the option is not selected, a specific value (from zone attribute) is regarded for each zone. Note SA = study area
Study area share	If you select the SA factor constant option, you can enter a value ≥ 0 for the intrazonal share for the mobility rate or for the attraction rate.

9. Confirm with OK.

10. Execute the procedure (Executing procedures in the procedure sequence).

EVA Trip generation is calculated and its results are saved per demand stratum to the zone attributes Productions and Attractions (Editing the demand of EVA-P demand strata).

Tips: You can display the results in zone lists (Viewing the demand of EVA-P demand strata in lists) or in the network graphics (Displaying data graphically and in lists). If you make the appropriate setting before opening a zone list (Setting list options), Visum will automatically create some list layout files when a zone list is opened. Using these files, you can quickly view the most important demand data.

Furthermore, you can use an add-on to generate a statistical overview of all results in tabular form (Running script files). The values gained for number of persons, structural properties, mobility and production rates as well as the demand calculated on this basis you can check for plausibility this way. You can find the add-on EVA analysis provided with the program under Scripts > Script menu > VisumAddIn > Demand.