[zang]

The thing I am confused about is the signals already can detect trains, because they have conditional TSP that only activates if the trains are behind schedule. Why is lidar technology required for phase rotation but not green extension?

I'm going to assume the already-existing signal interruption isn't on-board trains or at intersections, and may have to connect to a third-party system (ie; the city's traffic light control) rather than actual detection at intersections, which is what lidar would be (also, a single point of failure, not potentially three; likely making it safer)