train collision due to unsafe rail signal state

[namdre]

vehicles waiting at a red signal do not set approach information beyond that signal. Thus a protecting switch is assumed to have no approaches. If that signal turns green in the same step, the switch is wrongly assumed to give protection.

[namdre]

possible solution: if two signals switched to green in the same step and have an approaching vehicle, perform a driveway compatibility check and retract one of the switches (must happen after all tls events have been handled).