Calculating tour-based model - combined trip distribution and mode choice

Note: This function is only available if you have activated the Tour-based demand model add-on (Enabling or disabling add-ons).

For each transition in an activity chain, the Tour-based model - Combined trip distribution and mode choice calculates an overall demand matrix and mode-specific demand matrices simultaneously (Fundamentals: Tour-based model: trip distribution / mode choice combined).

1. Make sure, that the zone-specific demand by demand stratum is available as zone attribute Home trips (Calculating Tour-based model - Trip generation and Editing the demand of tour-based demand strata).

2. Make sure that - to each person group the Tour-based model - Trip distribution and Mode choice is to be calculated for - a demand matrix has been allocated to which the results are to be stored (Creating demand matrices for tour-based model - trip distribution and mode choice).

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

The Procedure sequence window opens.

4. To the procedure sequence, at the position of your choice, add the Tour-based model - Combined trip distribution / mode choice procedure of the Demand model category (Setting up and starting the procedure sequence).

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

The Demand strata selection Tour-based model window opens.

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

7. In the Demand strata list, click the demand strata for which you want to calculate the Tour-based model - Combined trip distribution and mode choice.

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

Alternatively, you may pre-select corresponding demand strata for certain person groups and activity pairs. Therefore, select the desired demand objects in the Person groups and Activity pairs selection lists and click the Confirm preselection button.

8. Confirm with OK.

The demand strata selected are listed in the DStrata input field and in the Reference object(s) column.

9. Make sure the added procedure is highlighted. Then, in the Operations section, click the Edit button.

The Parameters: Tour-based model - Combined trip distribution / mode choice window opens.

10. Make the desired changes.

Note: If within a row, data is missing that is required for the calculation, Visum highlights the fields in red. If you, e.g., choose to save a utility matrix, you must specify an output matrix. Otherwise, the filed in the Utility output matrix is highlighted in red.

Distribution utility tab
Element	Description
Maximum number of iterations	Number of iterations as a termination criterion if the procedure cannot reach convergence with the selected iteration algorithm.
Precision factor	Factor of precision for constraints (Properties and options of activities)
Key	Unique value generated by Visum for each combination of Person group and Activity.
Person group	Person group of the trip distribution
Activity	Destination activity of the trip distribution
Utility definition	Via this button, you may - in a separate window - define a combination of matrices and attribute vectors which will be used as utility matrix for the particular person group and activity during Trip distribution (Setting utility function parameters for tour-based model - trip distribution or tour-based model - mode choice).
Function type	Type of the utility function for trip distribution calculation (Fundamentals: Tour-based model: trip distribution / mode choice combined) For selection, use the selection list. Note The function type can be set individually or for a combination of person groups and activities. To do so, select the desired combination by holding down the Ctrl key and clicking on the desired rows.
a, b, c	Utility function parameters for trip distribution (Fundamentals: Tour-based model: trip distribution / mode choice combined) Depending on the selected function, parameters that are irrelevant for the respective function are grayed out.
Graph	Use this button to open a separate window in which you can show and edit the curve progression of the utility function (Viewing and editing the curve progression of the utility function).
Save utility matrix	Select this option to save the destination choice utility matrix.
Utility output matrix	Using the button opens the window Select matrices, where you can choose an output matrix, in which the destination choice utility matrix is saved (Selecting matrices).
Utility output matrix	Reference to the matrix which was selected using the button and the combination of matrix number and matrix name. If a matrix is not yet present, because it is only generated during the procedure, the field remains blank.
	In the Save utility matrix column, use the respective symbols to select all highlighted rows or undo the selection.
	Click the symbol to create a new output matrix for the row selected if, in the Utility output matrix column, no output matrix is specified.

Mode choice utility tab
Element	Description
Mode choice: Define utility per destination activity	Select this option to specify a different parameter for each destination activity. Select this option to show an additional Activity column in the Mode choice utility tab. For each destination activity, you can now specify a separate utility function (Setting utility function parameters for tour-based model - trip distribution or tour-based model - mode choice).
Calculate mode choice with Nested Logit model	If the option has been selected, you can calculate the mode choice with a Nested Logit model. You define a decision tree for the calculation of the mode choice (Nested Logit model: Edit decision tree). You can specify other settings on the Mode choice utility tab (Tour-based model: trip distribution / mode choice combined).
Decision tree	Click the button to open another window, in which you can edit the decision tree for the calculation using the Nested Logit model (Nested Logit model: Edit decision tree). Note The button is only available if the Calculate mode choice with Nested Logit model option has been selected.
Key	Unique value generated by Visum for each combination of Person group and Mode. Note If the option Mode choice: Define utility per destination activity has been selected, the key also contains the Activity.
Person group	Person group of mode choice
Activity	Destination activity of mode choice Note This option is only available for the utility function of the mode choice if you have selected the Mode choice: Define utility per destination activity option.
Mode	Mode selected
Mode / Nest	Selected mode with nests Note The column is available only if you have selected the option Mode choice: Define utility per destination activity.
Utility function	Via this button, you may - in a separate window - define a combination of matrices and attribute vectors which will be used as utility matrix for the particular person group and mode during Mode choice (Setting utility function parameters for tour-based model - trip distribution or tour-based model - mode choice).
Scaling parameters	This column is available if you have selected the option Calculate mode choice with Nested Logit model (Tour-based model: trip distribution / mode choice combined).
Allocation parameter	This column is available if you have selected the option Use nested logit model for mode choice and also calculate with cross nested logit (Tour-based model: trip distribution / mode choice combined).
Function type	Type of utility function for mode choice calculation (Fundamentals: Tour-based model: trip distribution / mode choice combined) For selection, use the selection list. Note The function type can be set individually or for person group and mode combinations. To do so, select the desired combination by holding down the Ctrl key and clicking on the desired rows.
a, b, c	Utility function parameters for mode choice (Fundamentals: Tour-based model: trip distribution / mode choice combined) Depending on the selected function, parameters that are irrelevant for the respective function are grayed out.
Graph	Use this button to open a separate window in which you can show and edit the curve progression of the utility function (Viewing and editing the curve progression of the utility function).

In the procedure, you can use what is known as rubber banding. This functionality allows the setting of trip chains that are aligned to a previously defined main activity. The rubber banding weight determines how strongly the impedances of the path legs are weighted between the intermediate activity and the main activity compared to the other path leg.

Rubberbanding tab
Element	Description
Use rubber banding	If the option is selected, rubber banding is used for the activity chain (Fundamentals: Using the rubber banding function for trip distribution)
Rubberbanding weight	Enter a number. The greater the value you enter, the stronger the rubber banding effect. A value of 1 means that both path legs are equally weighted. A value of 0 is tantamount to a calculation without rubber banding. We recommend values between 0.5 and 2.

Note: In the Activity chain with main activity column, the main activity is displayed in square brackets (Properties and options of activities). The lowest value in the Rank field defines the main activity. Since only one activity is considered the main activity, we recommend to allocate the lowest value to one activity. If there are several activities with the same lowest value, Visum automatically uses the first activity as main activity. The Activity chain with main activity column is highlighted in this case.

Output demand matrices tab
Element	Description
Calculate	Select this option to have Visum calculate a demand matrix for the combination of person group, modes, and activity chain of this table row.
Person groups	Click this button to specify the person groups of trip distribution for which you want to calculate an output matrix.
Modes	Click this button to specify the modes for which you want to calculate a matrix.
Origin activities	Click this button to specify the origin activities for which you want to calculate an output matrix.
Destination activities	Click this button to specify the destination activities for which you want to calculate an output matrix.
From time	Start time of the time interval, for which the calculation is to be performed (format: hh or hh:mm or hh:mm:ss)
To time	End time of the time interval, for which the calculation is to be performed (format: hh or hh:mm or hh:mm:ss)
Type	Shows the matrix type that is calculated. This data depends on the settings you made under Modes, Origin activity, and Destination activity. Distribution matrix You have selected all modes, origin activities and destination activities. Mode choice matrix You have no selected all modes, but all origin and destination activities. Activity matrix You have no selected all destination activities, but all origin activities and modes. Other For all other combinations of modes, origin activity, and destination activity
Output matrix	Using the button opens the window Select matrix, where you can choose the matrix in which the results are saved (Selecting matrices) .
Output matrix	Reference to the matrix which was selected using the button and the combination of matrix number and matrix name. If a matrix is not yet present, because it is only generated during the procedure, the field remains blank.

You can generate tours from the result of the tour-based procedure, which can be saved and visualized as path sequences. A tour represents an exemplary sequence of zones that a person could visit while completing an activity chain.

Note: This functionality is only available if you have activated the Multimodal and Tour-based demand model add-ons (Enabling or disabling add-ons).

Path sequences tab
Element	Description
Calculate departure times	If the option is selected, departure times are calculated for the path sequence items. Maximum number of iterations Number of iterations as a termination criterion if the procedure cannot reach convergence with the selected iteration algorithm. Maximum relative deviation The calculation of the departure times terminates if for all departure times, the relative deviation of the departure times between the current and the previous iteration is smaller than the specified value.
Compute path sequences	If this option is selected, path sequences are randomly calculated for the demand stratum from each zone.
Partitioning size	The number of path sequences to be generated per zone depends on the demand of the demand stratum at the zone and can be scaled separately for each demand stratum by the value of the partitioning size. The value indicates how many persons a path sequence corresponds to. For each demand stratum, N path sequences are determined from each origin zone, where: N = 1 / partitioning size * demand[DStrata,origin zone] Note N is rounded and can amount to a maximum of 65536.
Path sequence set	Drop-down list of the existing path sequence sets
Random seed	Start value of the random generator Note If you want to have exactly the same tours in all demand strata with the same distribution, you can set the random seed for all demand strata to the same value.
Generate missing path sequence sets	Use the button to generate path sequence sets for the demand strata, to which applies: the generation of path sequences is activated no path sequence set has yet been allocated

Note: For all activities of the selected demand strata for which path sequence sets are to be generated, missing path sequence activities are automatically generated by Visum.

You can use the symbols at the bottom section of the Output demand matrices tab to edit the table of output elements.

Icon	Name	Description
	Insert output element	Inserts a new row
	Copy selected output elements	Copies all rows selected
	Delete selected output elements	Deleted all rows selected
	Move selected output elements up/down	Moves all rows selected up/down
	Sort output elements in default order	Sorts the table in default order
	Calculate/Do not calculate selected output elements	In the Calculate column, use the symbols to choose all selected rows or undo the selection.
	Separate output matrices for selected output elements...	Click this button to create the table using the output matrices of your choice. In the table, select the rows of your choice and click the respective symbol. Then choose one of the following options: Separate matrices per person group A separate row is created for each person group. Entries in the Modes, Origin activities, and Destination activities columns are adopted. Separate matrices per mode A separate row is created for each mode. Entries in the Person group, Origin activities, and Destination activities columns are adopted. Separate matrices per origin activity A separate row is created for each origin activity. Entries in the Mode, Person group, and Destination activities columns are adopted. Separate matrices per destination activity A separate row is created for each destination activity. Entries in the Modes, Person group and Destination activities columns are adopted. Tip To easily set up a table, in the empty table, click the symbol to insert a default row. The default row contains all person groups, modes, origin activities, and destination activities. Using the options described, you can extend the default row to create the table required.
	Inserting missing matrices for selected output elements	Click the symbol to create a new output matrix for the row selected if in the Output matrix column, no output matrix is specified.

11. Confirm with OK.

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

Tour-based model - Combined trip distribution and mode choice are calculated for the time interval specified. The results for trip distribution are saved to demand matrices per person group and target activity. The results for mode choice are saved to demand matrices per person group and mode (Creating demand matrices for tour-based model - trip distribution and mode choice).

Tip: You can show and edit the demand matrices (Managing, showing and analyzing matrices).

Note: If you want to calculate the demand matrices for multiple time intervals you need to execute the Tour-based model - Combined Trip distribution and Mode choice repeatedly and to set various demand matrices to which the calculation results per time interval are to be saved.

Setting utility function parameters for tour-based model - trip distribution or tour-based model - mode choice

1. Open the Parameters: Tour-based model - Combined trip distribution/mode choice window (Calculating tour-based model - combined trip distribution and mode choice).

2. Click the Distribution utility or Mode choice utility tab.

3. For the desired person group, click the corresponding Utility definition button .

The Utility definition for person group/destination activity <key> or Utility definition for person group/mode <key> window opens.

Note: If you selected the option Mode choice: Define utility per destination, in the Mode choice utility tab, the window Utility definition for person group/mode/destination activity <key> opens. Then you can specify a separate utility definition for each destination activity.

4. Make the desired changes.

Element	Description
Utility U =	In this window, click the desired linear combination of matrices, attribute vectors and/or constants (Combining matrices and attribute vectors in the Matrix editor window). The utility function of trip distribution also contains the LogSum of mode-specific utility (as the first term) that you can multiply by a factor.
Transformation drop-down list	In the list box, click the function you want to use to transform the final combination result (result matrix) (Editing matrix values).
Input field formula	In this input field, define the remaining components of the utility function as a formula made of Visum skim matrices, zone attributes or constants (Creating a matrix calculated from a formula and Insert matrices via matrix reference).
	Use the icons to move up or down in the list of utility functions of the selected tab in the Parameters: Tour-based model - Combined trip distribution / mode choice window.

5. Confirm with OK.

The changes are applied.

Viewing and editing the curve progression of the utility function

1. Open the window Parameters: Tour-based model - Combined trip distribution / mode choice and select the Distribution utility or Mode choice utility tab (Calculating tour-based model - combined trip distribution and mode choice).

2. For the desired person group, click the corresponding Graph button.

The Function graph window opens. The curve progression of the utility function is shown with the currently set parameters a, b, and c.

3. In the Range section, you may edit the scaling of the x axis and the y axis, if applicable.

Element	Description
X Min	Minimum value for x-axis (negative values allowed)
X Max	Maximum value for x-axis
Y Min	Minimum value for y-axis (negative values allowed)
Y Max	Maximum value for y-axis
Apply	Click this button to use the entered values for the graph and to update the curve progression.

4. If required, in the Parameters section, edit the parameters a, b, and c of the utility function.

Tip: Alternatively, edit the parameters in the Distribution utility or Mode choice utility tab (Calculating tour-based model - combined trip distribution and mode choice).

5. Click the Apply button.

The entered parameter values are applied to the graph and will thus update the curve progression.

6. Confirm with OK.