For the headway-based procedure, each line is described by the line route, the run times between line stops, and the headway. Actually, it is the time profile which comprises this information and the headway-based procedure works on this model level (Network objects of the line hierarchy). In the following sections the term line is used for the sake of convenience. This emphasizes that the timetable of the individual vehicle journeys is not regarded.
Transfer wait times are usually regarded globally, which means that the departures of different lines are independent of each other. As a standard, a timetable coordination is not taken into consideration. By explicit modeling, however, it can be expressed that lines operate with the same headway each on a shared section, or rather a fixed transfer wait time exists between two lines (Matched transfers). TSys of the PuT-Aux type are not yet regarded.
The headway-based assignment procedure includes the three operational steps.
1. Headway calculation (Headway calculation)
2. Route search and route choice (Route search and Route choice)
3. Route loading
In the combination of search and choice, the headway-based procedure differs from the timetable-based assignment. In this second step, possible paths between two traffic zones are detected and simultaneously a distribution is specified between them. The paths do not represent connections, but routes (PuT paths), as the calculation is not done on the time axis, but merely regards travel times and headways. In the third step, the routes found in the search are loaded with the demand from the demand matrix and stored in memory (if desired).
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Note: In the directory C:\Users\Public\Documents\PTV Vision\PTV Visum 2021/Examples, you can find an example of use on this topic. The PuT Capacity Restrained/ Headway-based example demonstrates the application and effect of capacity restrictions in headway-based public transport assignment. |
