By default, the timetable-based assignment determines a connection's attractiveness without taking the demand into account. Accordingly, the demand is distributed onto possible connections without consideration of the vol/cap ratios of these connections. Regarding also the vol/cap ratio can return those connections as attractive alternatives which in the standard case seemed to be not attractive. Thus, the enhancement with this criterion might change the set of possible connections.
Basically, neglecting the capacities is a simplification, which unsatisfactorily reflects reality in highly loaded public transport systems. Capacity restrictions in practice can take effect in different ways:
- Fail to board: A vehicle can only take as many passengers as there is capacity.
- Discomfort in the vehicle: Passengers feel rather uncomfortable when traveling in a heavily loaded vehicle. This effect may be enhanced if there are no more seats available. The travel time in such vehicles is perceived as longer and more strenuous.
- Discomfort outside of the vehicle: Passengers feel rather uncomfortable when transferring at highly frequented stops. Besides unpleasant effects due to overcrowding, additional delays may occur.
The capacity restriction in the timetable-based assignment can be considered either hard or soft:
- The prevented boarding is the hard capacity restriction.
- The discomfort in the vehicle, i.e. not being able to find a seat or having to stand in a crowded place, is the soft capacity restriction.
The capacity-restricting effects at stops are not considered.
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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 Demand PuT Capacity example describes ways to consider public transport capacity restrictions in demand models. |
