Trip distribution means the determination of a total demand matrix per demand stratum from available productions and attraction of the individual zones by means of relevant skims (e.g. journey times, fares) (Fundamentals: Trip distribution).
Trip distribution is calculated with the help of the gravity model (Fundamentals: Gravity model calculation). You can estimate the gravity model parameters in advance (Estimating gravitation parameters (KALIBRI)).
1. Make sure that for each zone, the production and attraction rate per demand stratum are available as zone attributes Productions and Attractions (Starting the iterative repetition and Editing the demand of Standard 4-step demand strata).
2. On the toolbar, click the 
Open 'Procedure sequence' window button.
The Procedure sequence window opens.
3. To the procedure sequence, at the position of your choice, add the procedure Trip distribution of the Demand model category (Setting up and starting the procedure sequence).
4. In the row of the added procedure, click the button in the Reference object(s) column.
The Demand strata selection window opens.
5. In the Select demand model list, click the demand model the demand strata belong to.
6. In the Demand stratum selection list, select the demand strata you would like to calculate the trip distribution for.
|
Tip: To select multiple demand strata, hold down the Ctrl key while clicking the desired entries one by one. |
7. Confirm with OK.
The demand strata selected are listed in the Reference object(s) column.
8. Make sure the added procedure is highlighted. Then, in the Operations section, click the Edit button.
The Parameters: Trip distribution window opens.
9. Make the desired settings.
|
Element |
Description |
|
For active OD pairs only |
If this option has been checked, only those relations which are in the active state are considered (Exception: Filter for OD pairs). |
|
Exclude OD pairs connecting passive zones |
If this option has been selected, only OD pairs between active zones are considered (Using filters to set network objects active or passive and Setting network objects active/passive via the spatial selection). |
|
Set any result demand matrix to 0 prior to calculation |
If this option has been selected, all demand matrices allocated to the demand strata are set to 0 prior to summing up the calculated OD demand. Note You should check this option if trip distribution is to be calculated for all demand strata allocated to the same demand matrix. |
|
Apply estimated parameters |
|
|
Apply to all DStrata |
Use this button to apply the current combination of matrices and attribute vectors settings and the utility function set up for the currently selected activity to all other demand strata. |
|
Distribution matrix |
Reference to the demand matrix to which the trip distribution result is saved for the selected demand stratum and Selecting matrices)(Properties and options of demand strata. |
|
Function type |
Use the drop-down list to select the type of utility function you want to use for the calculation of the trip distribution. Note If you have selected the Apply estimated parameters option, the Logit option is grayed out. Tip Alternatively, you can specify the function type in the Options tab of the Choice model for <demand stratum> window. Use the |
|
Parameters |
a, b, c Estimated parameter values for the utility function modeling the response of travelers to distance or time conditions. The parameters can take negative values. Notes If you have selected the Apply estimated parameters option, the cells are grayed out. If the initial matrix contained impedance data such as distances or travel times, negative exponents need to be entered for the utility function. Tip Alternatively, you can specify the values in the Options tab of the Choice model for <demand stratum> window. Use the |
|
Direction parameters |
Use this option to select the distribution model to be calculated. Constrained production If this option has been selected, trip distribution is calculated singly-constrained for production. The Production zone attribute is taken into account for each zone. Constrained attraction If this option has been selected, trip distribution is calculated singly-constrained for attraction. The Attraction zone attribute is taken into account for each zone. Tip Alternatively, you can specify the values in the Options tab of the Choice model for <demand stratum> window. The window opens via the icon |
|
Distribution matrix |
Reference to the demand matrix to which the trip distribution result is saved for the selected demand stratum (Properties and options of demand strata). |
Select this option to use the parameters a, b, c and the function type of the demand stratum attributes.
If you do not select this option, specify the parameters and the function type per demand stratum in the list of demand strata.10. Click the 
(tooltip: Other parameters) button.
11. The Choice model for <demand stratum> window opens.
12. Select the Options tab.
|
Note: Only those items are described here that cannot be specified in the Parameters: Trip distribution window. |
13. Make the desired changes.
|
Element |
Description |
|
Doubly-constrained: Balancing by Multi procedure |
If this option has been checked, matrix balancing by multi-procedure is calculated additionally after the first iteration (Fundamentals: Projection). |
|
Matrix balancing according to ... |
Via this option you select the totals to be used for multi procedure calculation in case of different production and attraction totals (Fundamentals: Projection). Production total Multi procedure regards the production total. Attraction total Multi procedure regards the attraction total. Mean of both totals Multi-procedure uses the mean value calculated from production total and attraction total as a basis. Minimum of both totals Multi-procedure uses the smaller value of production and attraction totals as a basis. Maximum of both totals The multi procedure uses the greater value of production and attraction totals as a basis. Note This option is only provided for doubly-constrained balancing. |
|
Multi parameters |
Parameters for multi procedure calculation (Fundamentals: Projection) Maximum number of iterations: After the user-defined number of iterations the iteration process is canceled though convergence has not been reached yet. Quality factor: Criterion for termination of the multi procedure Note These options are only provided for doubly-constrained balancing. |
14. Select the Function graph tab.
The Function graph tab displays the curve progression of the utility function with the currently set parameters a, b and c.
15. 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. |
16. If required, in the Parameters section, edit the parameters a, b, and c of the utility function.
17. Click the Apply button.
The entered parameter values are applied to the graph and will thus update the curve progression.
|
Tip: To reset the utility function parameter values and the curve progression to default values, click the Reset button. |
18. Confirm with OK.
19. Click the Utility function button.
The Utility definition for demand stratum <> window opens. The utility corresponds to a result matrix which you can set for each demand stratum using your own formula.
20. Enter the desired formula (Creating a matrix calculated from a formula).
21. Confirm with OK.
The Parameters: Trip distribution window is displayed.
22. Click on the first column Distribution matrix.
The Select matrix window opens.
23. Select the demand matrix in which the result of the trip distribution for the selected demand stratum is stored. Two methods are available for this purpose (Selecting matrices)
| Element | Description |
|---|---|
|
Select matrix directly |
From the list of all matrices, select the desired matrix by its number. |
|
Select matrix by properties |
Select a matrix by certain attributes and their values. |
24. Confirm with OK.
The selected matrix is applied and displayed in the second column Matrix as a reference.
25. Execute the procedure (Executing procedures in the procedure sequence).
Trip distribution is calculated and its results are saved per demand stratum to the results matrix assigned.
|
Tip: You can view and edit the result matrices (Managing, showing and analyzing matrices). |
