Grade Crossing

Preemption Material

Railroad Crossing

Various factors contribute to the safety of a highway rail grade crossing near an intersection controlled by a traffic signal. A key factor is railroad preemption of the traffic signal. This page provides useful information for practitioners to understand the key elements of preemption as well as worksheets to calculate adequate advanced warning and preemption time. This information has been compiled from leading experts in both the public and private sectors to provide a robust resource for anyone who deals with highway rail at-grade crossings.

Seven Points Every Traffic Engineer Should Know About Rail Preemption Installations

  1. The presence of a nearby traffic signal has been identified in traffic safety studies as a leading indicator of grade crossing collisions...
  2. The old 200-foot rule has been expanded considerably...
  3. State of the art preemption requires more than a 2 wire connection...
  4. It is important to take into account the time required to provide proper service times to all of the movements in a preemption sequence...
  5. An “advance preemption” pulse may be required...
  6. Assure the automatic gates, if present, are in the horizontal position before the track clearance green is terminated...
  7. Even where no traffic signal is present, the presence of an intersection downstream from a grade crossing may require installation of a preempted traffic signal...

Read all of the details regarding the Seven Points Every Traffic Engineer Should Know About Rail Preemption Installations. (Source: Brent D. Ogden)

Recommended Practice

Preemption Forms

Knowing how much preemption time is needed is a key factor in signal timing near highway rail at-grade crossings. The following forms and instructions from the City of Los Angeles, Department of Transportation and the Texas Department of Transportation provide a methodology and worksheets to determine the adequate amount of preemption and advance preemption time needed.

City of Los Angeles Department of Transportation

Texas Department of Transportation

Institute of Transportation Engineers
1627 Eye Street, NW, Suite 600 | Washington, DC 20006 USA
Telephone: +1 202-785-0060 | Fax: +1 202-785-0609

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