• Preemption timing plans should consider the following: intersection geometry, highway-rail grade crossing geometry, approaches to the grade crossing, travel times to clear intersection/crossing, vehicle volumes, frequency of train movements, train stops within the approach to grade crossing, vehicle queue lengths, design vehicles, types of active warning devices, pedestrian activity [5].
• Clearance time is additional time provided to account for track features such as skewed grade crossings or other features that require additional time for vehicles to clear the crossing. This should be considered along with the number of large/slow vehicles that may typically utilize the crossing. The SCRRA recommends clearance time to be added to the minimum time at a rate of one second per 10 feet of MTCD exceeding 35 feet [1].
• Blank-out or Changeable Message Signs or other appropriate signal indications should be considered to prohibit left turns toward the grade crossing during preemption [2].
• “Preemption trap” is the condition where vehicles may be trapped within the MTCD due to improper timing of the preemption signal. Care should be taken to avoid this situation [5].
• Preemption may also be coordinated for other priorities such as emergency vehicles or transit vehicles. However, railroad preemption should always retain highest priority [3].

• Improves safety by clearing vehicles from grade crossings [3].

• Preemption requires additional coordination between highway agencies and railroad companies to fully understand the operation of systems [2].
• Advance preemption requires additional infrastructure improvements and results in increased installation and maintenance costs. Additionally, these improvements are typically paid for by railroad companies and thus require additional coordination [2].
• Installation of preemption system can be expensive.

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[1] Federal Highway Administration. (2009). Manual on Uniform Traffic Control Devices for Streets and Highways, 2009 Edition.

Document Excerpt: The Manual on Uniform Traffic Control Devices (MUTCD), by setting minimum standards and providing guidance, ensures uniformity of traffic control devices across the nation. The use of uniform TCDs (messages, locations, sizes, shapes, and colors) helps reduce crashes and congestion, and improves the efficiency of the surface transportation system. Uniformity also helps reduce the cost of TCDs through standardization. The information contained in the MUTCD is the result of years of practical experience, research, and/or the MUTCD experimentation process. This effort ensures that TCDs are visible, recognizable, understandable, and necessary. The MUTCD is a dynamic document that changes with time to address contemporary safety and operational issues.

[2] U.S. Department of Transportation. (2019). Highway-Rail Grade Crossing Handbook – Third Edition.

Abstract: The purpose of the Highway-Rail Crossing Handbook, 3rd Edition is an information resource developed to provide a unified reference document on prevalent and best practices as well as adopted standards relative to highway-rail grade crossings. The handbook provides general information on highway-rail crossings; characteristics of the crossing environment and users; and physical and operational changes that can be made at crossings to enhance the safety and operation of both highway and rail traffic over such intersections. The guidelines identified and potential alternative improvements presented in this handbook reflect current best practices nationwide.

[3] Texas Department of Transportation. (2015). Rail-Highway Operations Manual.

Excerpt: The Texas Department of Transportation (TxDOT) Rail-Highway Operations Manual is intended to cover responsibilities and best practices on projects that impact both roadway and railroad rights-of-ways. The manual defines both District and Division TxDOT responsibilities on the various types of projects encountered and coordination efforts required between railroad companies and other entities.

[4] Cambridge Systematics. (2018). Rail Strategy Study – Grade Crossing Toolkit.

Excerpt: The Grade Crossing Toolkit provides information and tools to identify candidate crossing improvements across a range of options. The Toolkit describes rail crossing treatments, such as grade separations, closures, consolidation, passive treatments, active devices, quiet zones, and specialized treatments for pedestrian/bicycle issues.

[5] Southern California Regional Rail Authority. (2021). SCRRA Highway-Rail Grade Crossings Recommended Design Practices and Standards Manual.

Excerpt: This Manual was developed in 2009 and issued as a Recommended Design Practices and Standards Manual.

Additional Resources

Institute of Transportation Engineers. (2019). Preemption of Traffic Signals Near Railroad Grade Crossings Recommended Practice, Second Edition.

Excerpt: 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.

Pre-signal

Queue cutter