The procedure calculates the destination and mode choice (Fundamentals: ABM Nested Demand).
1. On the toolbar, click the Open 'Procedure sequence' window button 
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The Procedure sequence window opens.
2. To the procedure sequence, at the position of your choice, add the procedure ABM Nested Demand of the Demand model category (Setting up and starting the procedure sequence).
3. Make sure the added procedure is marked. Then, in the Operations section, click the Edit button.
4. Make the desired changes on the Basis page.
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Element |
Description |
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General settings |
Calculate choice for main activity executions / Calculate choice for secondary activity executions Select whether you want to calculate the choice for main activity executions and/or secondary activity executions. Rank of activity executions The rank is used to determine the main activity execution within a tour: the activity executions with the lowest rank is the main activity execution. If there is more than one, the first one is chosen. Mode set Select the number of selectable modes. |
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Individual preferences |
Individual preferences are generated by Visum whenever they are needed for the calculation. However, if you want to create the individual preferences reproducibly, you must have them recalculated after model adjustments. The recalculation is only recommended for the demand calculation of the base case. A recalculation for a scenario destroys the stability function of the ABM Nested Demand. Random seed If the settings are otherwise unchanged, a different random seed will generate different individual preferences and therefore a different result. Recalculate individual preferences If the option has been selected, the individual preferences are recalculated. |
5. Make the desired changes on the ABM tour groups page.
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Element |
Description |
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Tour groups correspond to the demand strata in aggregated demand models. Add the desired tour groups individually or several at the same time. The tour groups defined here are referenced in all other tabs. In the Tour filter column, you can insert a freely editable formula expression for each tour group that describes the respective tour. Note You can copy selected tour groups to the clipboard via the shortcut menu. |
6. Make the desired changes on the Shortest path searches page.
Skims for determining the utility can be determined on the basis of shortest path searches. Parameters for these shortest path searches and the resulting travel times are defined here.
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Element |
Description |
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Allow internal traffic |
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Parameters per PuT mode |
TSys for origin and destination walk path Transportation system for the walk path from locations to stop areas and vice versa. Maximum walk path time The shortest path search only takes into account those stop areas that can be reached within the maximum walk path time. Impedance factor for walk path time For public transport paths, the impedance to be minimized in the shortest path search also includes the origin and destination walk paths to and from the stop areas. This is included in the impedance with the specified factor. |
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Impedance criterion and travel time for location-based shortest path searches |
Impedance attributes and attributes for the travel time are set for private transport modes, impedance matrices and matrices for the travel time are set for public transport modes. Impedance attribute In the private transport shortest path search, the shortest path search is searched for in relation to this impedance attribute. It must be available for the three path objects links, turns, and main turns (if available in the network). User-defined attributes are often used here (as in the ABM Nested Demand example of use). Note Restricted traffic have a special status: The impedance attribute may or may not exist for restricted traffic areas. Dynamic (i.e. time-dependent) attributes are indicated by an empty bracket. Time-dependent attributes, i.e. attributes with subattribute Analysis time intervals, are only permitted as user-defined attributes. Attribute for travel time Attribute of the shortest path that contains the travel time. The same conditions apply as for the impedance attribute. Impedance matrix A stop area matrix is provided for the public transport shortest path search. Time-dependent matrices are defined by matrix conditions such as [TOTIME]=CONTEXT[TOTIME]. Matrix for travel time Stop area matrix, which contains the travel time. Time-dependent matrices are defined by matrix conditions such as [TOTIME]=CONTEXT[TOTIME]. |
If this option is selected, shortest paths within a location are permitted.
If the option is not selected, there is generally no shortest path within a location, regardless of whether the shortest path is included in the utility definition or not.7. Make the desired changes on the Base utility page.
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Note: The utility is the sum of the rows. The value per row is in turn multiplied by the columns. The two tables are synchronized; the right-hand table shows the utility of the combination of tour group and mode marked in the left-hand table. You can use the symbols above the table on the right to insert additional utilities for each row. |
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Element |
Description |
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Activity execution factor |
An attribute of the selected activity execution or a derived relation. Notes The attribute value is evaluated at the beginning of the calculation. All attributes or relations that only become available in the course of the calculation must not be selected, as they are not yet known at the beginning. This applies in particular to the relation to the location. |
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Zone utility |
Matrix formula for the zone utility As is usual with matrix formulas, matrix, zone, and mode attributes can also be used via the context operator (e.g. CONTEXT[MODE\BETA]). Additional relations are not permitted, even if they are provided in the attribute selection window. The same applies to dynamic attributes. Time-dependent matrices are defined by matrix conditions such as [TOTIME]=CONTEXT[TOTIME]. If a zone utility is defined, all locations must be allocated to a zone (Properties and options of locations). |
| Location utility |
Utility on the level of location relations In private transport, this is the result of a shortest path search between the involved locations. In public transport, the walk time from the location to the stop area or from the stop area to the location can additionally be selected. |
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Shortest PrT path attribute |
Attribute of the shortest path (if selected accordingly in the location utility) It must be available for the three path objects links, turns, and main turns (if available in the network). Restricted traffic areas have a special position: The attribute does not have to be available for restricted traffic areas and attributes of the restricted traffic areas do not have to be available for the other path objects. Dynamic (i.e. time-dependent) attributes are indicated by an empty bracket. Only user-defined attributes that have analysis time intervals as a subattribute are permitted. Note Make sure that all skims are specified in the desired unit. Typically, the unit minutes is used. If the shortest path attribute is defined in seconds, the skims must be multiplied by 1/60 accordingly. |
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Matrix for shortest PuT path |
Stop area matrix Dynamic output matrices are referenced using the context operator, as with the zone utility. |
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Note: Using the |
symbols, you can easily export or import the utility definitions via the clipboard, for example to/from Microsoft Excel8. Make the desired changes on the Scaling parameters page.
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Element |
Description |
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Location choice lambda / Mode choice lambda |
Set the desired values for each tour group. Note If the location choice lambda is set higher than the mode choice lambda, a warning is issued. You can calculate with such lambda combinations, but according to common discrete choice theory, this does not correspond to a regular choice-making process and can lead to inconsistent choices. |
9. Make the desired changes on the Output page.
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Element |
Description |
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Output of the stop areas selected in the shortest path |
If required, select numerical attributes for the output of boarding and alighting stop areas. Notes If no attributes are selected, no stop areas are output. |
10. Confirm with OK.
11. Execute the procedure.
The destinations and modes of the trips are calculated. The results can be found in the trips list in the DSegCode attribute and in the list of activity executions in the location number attribute.
