When predetermining PuT Walk path legs for the headway-based or the timetable-based assignment, the shortest path search can be restricted to specific PuT Walk path legs. You may edit the settings for the transitions between stop areas and for the PuT Walk path legs between zones.
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Note: By default a transfer consists of a PuT Walk path leg between two stop areas. In some cases, a transfer event may also include links open for PuT Walk and/or even cross other stops. Therefore the term transfer is used in Visum for transfer events in general. |
1. From the Calculate menu, choose General procedure settings.
The General procedure settings window opens.
2. In the navigator, select PuT settings > Assignment.
3. In the Walk links section, make the desired settings.
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Element |
Description |
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Maximum walk time for access and egress |
Maximum duration of a walk for access and egress to and from the stop in minutes |
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Maximum walk time for transfers |
Maximum duration of a walk for a transfer A value of 0 results in no transfer walk links being searched in the network. The maximum walk time does not affect the walk links within a stop, the only exception being a value of 1440, which causes the transfer within the stop to be blocked. |
4. In the Walk links within a stop drop-down list, select the desired entry.
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Element |
Description |
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Search without restrictions |
Shortest path search accounts for all PuT Walk path legs of a network. Based on the stop matrix, Visum automatically determines all possible (even indirect) transitions and the most favorable transition for each pair of stop areas. In the process, it uses the combined time of an indirect transition instead of the direct transition if it is less than the direct time. For stop areas which are connected to the same access node, the transition time is 0 since each stop area without a time penalty is connected to its access node. Example According to the stop matrix, the transition from stop area A to stop area C takes 5 minutes. The transition from stop area A to stop area B takes 1 minute and the transition from stop area B to stop area C takes 2 minutes. In this case, Visum identifies a transition of 3 minutes for changing from stop area A to stop area C. Note The use of this option might lead to a multitude of possible (direct or indirect) paths in case of a large number of stop areas. The shortest path search is expensive in case of a large number of paths. However, we recommend using this option, as it is the only one that finds the shortest walk link (time) between two points in all cases. |
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Do not permit search via access node |
The shortest path search is restricted to PuT Walk path legs of the stop matrix. The transfer times are taken into account like for the search without restrictions; the access node, however, is ignored, so that the transfer time from the matrix is used for transfers between stop areas which have the same access node (direct or indirect). This does not cause changes to PuT Walk path legs between other network objects. Note When using this option and the option No search, use the matrix as specified, it cannot be guaranteed in all cases that a shortest walk link (time) will be found. You should therefore use this option carefully and check the results for plausibility. The background to this special behavior is: the local restriction of routing options in the search algorithm can lead to optimal paths being dominated by alternatives that are actually faster to reach the common end of the path, but cannot be continued to more distant points in a permitted manner (Example for searching walk links at stops). |
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No search, use the matrix as specified |
The PuT Walk path legs are generated exactly according to the entered transfer times. Visum does not determine indirect transfers. Any transfers for which no transfer times have been entered are prohibited. This setting possibly also has an effect on PuT Walk path legs between other network objects.
Example According to the stop matrix, the transfer from stop area A to stop area C takes 5 minutes. The transfer from stop area A to stop area B takes 1 minute and the transfer from stop area B to stop area C takes 2 minutes. Nevertheless, Visum would use 5 minutes for the transfer from stop area A to stop area C. This makes sense if, for example, streets have to be crossed for the indirect transfer or if the 'intermediate' stop area is not used, since it is located underground. Notes This option we recommend to experienced users only, since the user has to ensure that the matrix contains meaningful and matching entries. If the direct transfer time between two stop areas is much higher than the combined time, which would be needed for indirect transfers, Visum might find useless connections (Example for searching walk links at stops). |
5. In the Walk links section, select the desired entry in the Walk links from/to connectors drop-down list.
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Element |
Description |
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Permit all walk links |
Path search between two zones may detect pure walk paths. Therefore paths are also permissible, which use exclusively a PuT Walk TSys and do not contain a PuT path leg. |
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Walk links between zones not permitted |
Paths between two zones, which exist of just two connectors or of two connectors and a PuT Walk path leg, are ignored during the shortest path search. Path that use at least one PuT path leg (e.g. PuT line, PuT Aux, Sharing) are permitted. |
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Force boarding/alighting at connected node |
After the origin connector, it is mandatory to board at a stop area located at the node of the origin connector. The same applies for alighting at the node of the destination connector. |
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Notes: If either option Walk links between zones not permitted or Force boarding/alighting at connected node is selected, no connections without PuT are found between zones. In this case, the corresponding setting for the timetable-based assignment is irrelevant (Timetable-based assignment: Preselection page). Using the options Walk links between zones not permitted and Force boarding/alighting at connected node is only recommended for experienced users. |
6. Confirm with OK.
The changes are applied. The next PuT assignment will use the new settings.
Example for searching walk links at stops
The following example illustrates how the three options for searching walk links at stops work. The fastest walk link from origin stop area 21 to destination stop point 4 is to be found in the network section shown.
Image 285: Modeled network section
The Image 285 shows the modeled network section with the following elements:
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Element |
Description |
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Stop point (at node 2) |
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Stop |
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Stop area |
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Links with walk times |
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Walk times between stop areas |
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Access node of stop areas |
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Gray section |
Stop with stop point, stop area(s) |
The network modeling of bus stop 3 is very important:
- Node 6 is the access node for the stop areas 41 and 42.
- Stop point 4 is part of stop area 42.
- The respective transfer times are marked in red.
- The matrix for stop 3 is:
Image 286 shows in blue the shortest path found with the option Search without restrictions. It is 2 minutes, since each stop area is linked to its access node without a time penalty.
Image 286: Shortest path for search without restrictions
Image 287 shows in blue the shortest path found with the options 2 Do not permit search via access node and 3 No search, use the matrix as specified. It is three minutes.
Image 287: Shortest path for options 2 and 3
Reason:
For the search with option 2, the path 21 > 2 > 3 > 31 > 41 > 6 > 42 > 4 is not allowed, as section 41 > 6 > 42 is prohibited by the selected option. The stop may not be left and re-entered via the same access node.
The shortest path found leads via 21 > 2 > 3 > 31 > 42 > 4 and not via 21 > 2 > 6 > 42 > 4, although the second path is only 2min 30s. This is because path 21 > 2 > 6 is dominated by the faster path 21 > 2 > 3 > 31 > 41 > 6 and omitted in the shortest path search.
The search with option 3 leads to the same result as with option 2, since there is no matrix entry for path 41 > 42, so this path leg does not exist according to the matrix.
