Several questions, regarding traffic signal preemption at a grade crossing
- Is the preempt relay, which triggers the preemption sequence, located inside the bungalow which houses the grade crossing predictor, or is it located inside the cabinet which houses the traffic signal controller?
- It is my understanding that the speed of an approaching train determines the length of time that the preemption sequence will be provided for. Is that true? And if so, does the crossing predictor calculate the train's speed, determine how long the preemption should be provided for and then tell the traffic signal controller to provide it for that amount of time?