The City of Milpitas, California, wanted to integrate its new light rail system (Figure 1) with traffic light controls at four different 4-way intersections. The City wanted the trains to be able to pass through each intersection safely without slowing or stopping for auto traffic in normal operation. They also wanted to be able to tell the trains to stop when dictated by certain traffic signal and pedestrian conditions. Ideally, the new automation system would sense the approach of a train, change the traffic signals to stop cross traffic, and allow the light rail train to pass through without slowing.
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