Traffic signals near railroad grade crossings can be connected to the railroad equipment to initiate a traffic signal preemption sequence. The railroad installs sensors on the tracks that send an electrical input to the traffic signal controller as the train passes over the sensors.

When To Use.

Preemption of a traffic signal by the railroad signals is required if the traffic signal is at an intersection that is within 200 feet of a railroad grade crossing. Preemption should be considered wherever traffic may back up over the crossing due to traffic signals or other traffic congestion.

Traffic signal preemption requires an agreement with the railroad. For more information on railroad agreements and preemption, see the

Rail-Highway Operations Manual

.

Types of Railroad Preemption.

Preemption of a traffic signal by railroad equipment may be either “simultaneous” or “advance.” These terms, which are used by the railroads, are explained in the

Rail-Highway Operations Manual

.