ITE Journal - June 2021 - 21

inside ite  | RESOURCES

Preemption of Traffic Signals
Near Railroad Grade Crossings
Purpose and Intended Use

Where a signalized intersection is in close proximity to a railroad crossing and either queues
from the intersection impact the crossing or queues from the crossing impact the intersection,
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 report is written primarily for an audience of 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 current state-ofthe-practice, and a balance between sound engineering theory and practical application.

The Institute of Transportation
Engineers (ITE) has completed
preparation of the final version
of Preemption of Traffic
Signals Near Railroad Grade
Crossings (RP-025D) which
was been adopted by the ITE
International Board of Direction.

The Recommended Practice

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 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 the distance and methods for estimating queue lengths.
*	 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 as well as the 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 maximum preemption timer, motion-sensing detection circuits, and simultaneous versus advance preemption operation.
*	 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, pedestrian hybrid beacons, and 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. itej

Availability and
Information
The publication may be purchased through the
ITE Bookstore as an ePublication (Member $75
| Non-Member $150) and a limited number in
print (Member $100 | Non-Member $175)
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 is consistently reflected.
w w w .i t e.or g

J u ne 2021

21
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ITE Journal - June 2021

Table of Contents for the Digital Edition of ITE Journal - June 2021
