On the one hand, it may be desirable that an early PT is not prioritised. On the other hand, a PT that is too late may no longer be prioritised. For this reason, the first step is to check the type of prioritisation required, irrespective of the conflicting requirements. This decision should be made on the basis of the timetable position criterion:
Figure 24: Changing the priority class
In contrast to the other traffic stream types, a PT traffic stream can be defined in several priority classes in the main series. vs | plus checks which priority class the PT traffic stream is to be treated in as part of the "Prioritisation tests" function based on the timetable position and the defined limits.