A bus or tram may be delayed, for instance, by traffic, or because there are a lot of travelers. If a driver sees that a bus or tram is very close behind, the driver will pass a stop to catch up on lost time.
It is also possible that a bus or tram has been delayed so much that further action is needed. GVB traffic control may then instruct the driver to cover part of the route without picking up passengers to get back on the right timetable as soon as possible. This may seem unfriendly towards our clients at the stops, but it is the best way to guarantee a reliable timetable.