Preemption of Traffic Signals Near Railroad Grade Crossings Recommended Practice, Second Edition
The final version of Preemption of Traffic Signals Near Railroad Grade Crossings (RP-025D) has been adopted by the ITE International Board of Direction.The recommended practice is now available in the ITE Bookstore in a PDF ePub Version.
Purpose and Intended Use
Where a signalized intersection exists in close proximity to a railroad crossing—and either queues from the intersection impact the crossing, or queues from the crossing impact the inter- section—the railroad signal control equipment and the highway traffic signal control equipment should be interconnected. The normal operation of the traffic signals controlling the intersection should be preempted to operate in a special control mode when trains are approaching. While public agencies have practices or procedures on the preemption of traffic signals near railroad grade crossings, there have been significant advances in engineering and technology since the last edition in 2006. The goal of the recommended practice is to reflect the current state-of-
the-practice and to provide the user with a broad overview of key considerations. The report is written primarily for engineers working for public agencies, railroads, and public transit agencies engaged in signal design and operational timing. ITE’s intent for the recommended practice is to reflect a balance between sound engineering theory and practical application.
The Recommended Practice
The final recommended practice was updated in response to comments received on the proposed versions of the document. The report includes new information on the design and operation of traffic signal preemption that has been developed since the previous edition was published, including:
- The concept and the function of diagnostic teams including the role of the railroad signal engineer.
- Explanation of the critical factor for determining the need for preemption is not the distance to the crossing, but the likelihood that a traffic queue will extend onto the tracks, regardless of what the distance is. Additional methods for estimating queue lengths are provided.
- New definitions have been added as well as new drawings illustrating the definitions of the Clear Storage Distance and the Minimum Track Clearance Distance.
- Illustrated explanation of the procedure for preempting traffic signals of diagonal grade crossings at intersections.
- Illustrated discussion of use of pavement markings to warn drivers of the area of a railroad crossing to not block.
- Additional discussion on the need for special traffic control when there is construction in the vicinity of a railroad crossing consistent with the requirements of the MUTCD.
- Discussion of simultaneous versus advance preemption operation;
- Supplements discussion on the maximum preemption timer and modifies text regarding motion-sensing detection circuits;
- Detailed information regarding the use of pre-signals and queue-cutter signals as well as hybrid systems for long distances between the traffic signal and the railroad crossing.
- Expansion of the section on the design of preemption interconnection circuits types relative to current standards.
- Discussion of ADA considerations.
- Supplemental information regarding the timing of traffic signal preemption to accommodate pedestrians.
- New information regarding the need for preemption of flashing beacons or hybrid beacons at pedestrian grade crossings.
- References to preemption timing worksheets from two roadway jurisdictions as methodological examples.
- Includes updated figures as well as other technical and editorial revisions to improve readability and clarity throughout.
The development of the recommended practice was coordinated with the Highway-Rail Crossing Handbook, 3rd Edition and incorporates references to the most recent edition of the American Railway Engineering and Maintenance of Way Association Communications and Signals Manual of Recommended Practice so that the information will be consistently reflected.