In the procedure EVA trip distribution and mode choice, Visum calculates demand matrices on the basis of each zone's production and attraction determined in the trip generation step. Those matrices contain the number of trips between two zones each by demand stratum and mode. In contrast to the Standard 4-step model, the calculation of trip distribution and mode choice is performed simultaneously in an interlinked procedure. Two different iteration algorithms are provided for the approximate calculation (Fundamentals: EVA trip distribution and mode choice).
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 EVA distribution/mode choice procedure of the Demand model category (Setting up and starting the procedure sequence).
3. In the row of the added procedure, click the button in the Reference object(s) column.
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 list, click the demand strata for which you want to calculate EVA trip distribution and mode choice.
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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 DStrata input field and in the Reference object(s) column.
7. Make sure the added procedure is highlighted. Then, in the Operations section, click the Edit button.
The Parameters EVA distribution/mode choice window opens.
8. Select the General parameters tab.
9. Make the desired changes.
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Element |
Description |
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Project type |
Via this option, you decide how to handle the mode shares Analysis You use the analysis to calculate the balance factors for mode choice. Select this option to enter the global mode shares of the total demand in the Standardized assessment tab. Forecast Select this option to use the existing balance factors for mode choice as a basis for calculation (Fundamentals: EVA trip distribution and mode choice). |
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Execute balancing |
If this option has been checked, balancing is performed at the end of EVA Distribution and Mode choice (Fundamentals: EVA trip distribution and mode choice). Notes This option is only available if you have selected balancing for a demand stratum. You can define the demand stratum (OD type 3) for which to compute balancing on the Constraints tab under Demand > Demand models (Defining constraints). If balancing has already been calculated at the end of the EVA Trip generation step, it is not calculated anew at this point (Calculating EVA trip generation). |
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Maximum number of iterations |
Number of iterations as a termination criterion if the procedure cannot reach convergence with the selected iteration algorithm. |
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Tolerance for hard constraints |
Factor of precision for hard constraints (Fundamentals: EVA trip generation) |
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Tolerance for non-hard constraints |
Factor of precision for non-hard constraints (i.e. Soft, Elastic or Open) (Fundamentals: EVA trip generation) |
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Use saved balance factors as initial solution |
Note This option is available after you select the project type Analysis.
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Use saved balance factors for productions and attractions as initial solution |
Note This option is available after you select the project type Forecast.
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Store calculated balance factors for productions and attractions |
Note The balance factors for mode choice are always saved during analysis, but not during the forecast! |
Select this option to include the existing balance factors for productions, attractions and mode choice in the calculation 
If you do not select this option, the balance factors will not be taken into account for calculation.10. Select the Procedure tab.
11. Make the desired changes.
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Element |
Description |
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Procedure |
Via this selection list, you may - for each demand stratum - select the iterative procedure for solving the trilinear equation system (Fundamentals: EVA trip distribution and mode choice). |
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Fixing |
For acceleration of the multi procedure convergence you may fix either productions or attractions - thus, these remain constant during the iterative procedure. From the selection list, select the type of fixing. Note This option is only provided for the Multi procedure. |
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Tip: You can adopt the entries made in one row for all other rows. To do so, right-click the row of your choice and select Use all attributes for all demand strata. |
12. Select the Standardized assessment tab.
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Note: The Standardized assessment tab is only provided if - in the General parameters tab - option Analysis has been selected for project type. |
13. For each mode, specify the mode's share of the total demand of the demand stratum.
14. If applicable, click the Standardize rows button.
For each demand stratum, all shares are standardized in such a way that their sum amounts to 1.
15. Select the Mode choice matrices tab.
16. In the desired row, click the button in the first column Mode choice matrix.
The Select matrix window opens.
17. Select the matrix you want to add the respective demand to during mode choice. Here, two methods are provided (Selecting matrices).
| Element | Description |
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Select matrix directly |
From the list of all matrices, select the desired matrix by its number. |
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Select matrix by properties |
Select a matrix by certain attributes and their values. |
18. Confirm with OK.
The demand matrix is allocated to the mode. A reference to the selected mode choice matrix will be displayed in the second column ModeChoiceMatrix.
19. In the same way, select the matrix of your choice for all demand strata.
20. Confirm with OK.
21. Execute the procedure (Executing procedures in the procedure sequence).
EVA distribution and mode choice are calculated and their results are saved per demand stratum and mode to separate demand matrices.
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Tips: You can show and edit the demand matrices (Editing matrix values). For plausibilization of results we recommend to create a trip length distribution by classification of demand matrices with the help of a skim matrix coding the distance (Showing matrices in a histogram). |
