Coordinating light-rail trains, traffic lights

摘要

The City of Milpitas, Calif. wanted to integrate its new light-rail system with traffic light controls at four different four-way intersections (see Figure 1). The city wanted the trains to be able to pass through each intersection safely without slowing or stopping for vehicular traffic in normal operation. It 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 should be able to 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.