Improved Highway-Railway Interface for the Preempt Trap

Document Type

Journal Article

Publication Date


Subject Area

operations - traffic, infrastructure - right of way, infrastructure - bus/tram priority, infrastructure - traffic signals, mode - rail, mode - bike


Traffic signal priority systems, Traffic signal preemption, Traffic signal cycle, Right of way (Traffic), Railroad grade crossings, Preemption (Traffic signals), Preempt trap, Level crossings, Highway railroad grade crossings, Highway rail intersections, Grade crossings, Cycle (Traffic signals)


Railroad preemption is intended to improve safety at highway–railway intersections by minimizing the likelihood that a vehicle will become trapped on the crossing. However, unless sufficient time is provided to transfer right-of-way safely from the currently operating highway traffic phase, preemption can cause safety problems for highway users. Advance preemption has been used to address right-of-way transfer time issues without making the railroad warning time excessively long. The use of advance preemption without proper precautions can lead to the preempt trap. A new approach that uses improved communication has been developed and implemented to address the needs of all users at and near the highway–railway intersection. The results of a field implementation in Los Angeles, California, demonstrate the effectiveness of the new approach.