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The Institute of Transportation Engineers (ITE) prepared this report to reflect the current state-of-the-practice and to provide the user with a broad overview of key considerations for the preemption of traffic signals near railroad grade crossings. 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 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. This proposed recommended practice was written primarily for an audience of engineers working for public agencies, railroads, and public transit agencies engaged in signal design and operational timing. The objective of this proposed revision is to include new information on the design and operation of traffic signal preemption that has been learned since the previous edition was published.
ITE prepared this recommended practice to reflect the current state-of-the-practice and provide the user with a broad overview of key considerations for the preemption of traffic signals near railroad grade crossings. In these locations the railroad signal control equipment and the roadway traffic signal control equipment should be interconnected and normal operation of the traffic signals controlling the intersection should be preempted to operate in a special control mode when trains are approaching. 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.
Presents a review of the current practices associated with the operation of traffic signals at intersections located near highway-rail grade crossings.
This report discusses current issues and technological advances, identifies as many elements as possible, and lists references, where feasible, to provide a contemporary resource for the designer, operator and administrator of an interconnected, preempted traffic signal near a highway-railroad grade crossing with active warning devices.
The Texas Department of Transportation (TxDOT) primarily uses simultaneous preemption of traffic signals near highway-rail grade crossings to clear queued vehicles prior to the arrival of a train at the crossing. At some intersections, 20 seconds of advanced warning may not be sufficient to allow the traffic signal to clear pedestrians using the normal clearance intervals between phases. The research developed an alternative method (non-vital advance preemption) of ensuring adequate pedestrian clearance in the presence of an approaching train without interfering with the normal preemption sequence at the intersection or installing costly additional track circuitry needed to provide advance preemption. Two strategies were investigated to ensure pedestrian clearance time. The first utilizes a lower-level preemption sequence to guarantee full pedestrian clearance to a terminating phase before the traffic signal starts the preemption sequence. The second strategy uses the pedestrian-omit feature to prevent the controller from activating the pedestrian interval if there is not sufficient time in advance of the start of the preemption sequence to provide full pedestrian clearance.