Traffic signals near railroad grade crossings having active warning systems are normally interconnected and receive a signal from the railroad track circuitry when trains are approaching. This train approach signal is used by the traffic signal to interrupt and preempt its normal phasing and enter into higher priority special phasings to clear the track of any vehicles that might be stopped in the pathway of a train. The amount of preemption time needed to clear a vehicle from the pathway of a train is necessary information for appropriate preemption signal settings but there are no definitive guidelines on how to determine this amount of time. It is usually left to the judgment of the signal engineer, and frequently unfounded assumptions are used. This study investigated the time required to clear a vehicle in a queue backed up onto a track at railroad-preempted traffic signals. The two key time components are start-up delay and repositioning time. Queues where all preceding vehicles are short passenger cars cause the longest start-up delays, and heavy trucks at the track involve the longest repositioning times. The model developed is convenient because once it is decided that preemption is needed, only easily determined values are required—the minimum track clearance distance, the clear storage distance, and the types of vehicles that are permitted to use the roadway. The model adopts a high level of confidence to minimize the risk of crashes but avoids the "worst-case" concept to avert an invitation for litigation when an improbable or unforeseen worst case results in a crash.


    Access

    Download

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Easy-to-Apply Solution to a Persistent Safety Problem: Clearance Time for Railroad-Preempted Traffic Signals


    Additional title:

    Transportation Research Record


    Contributors:
    Long, Gary (author)


    Publication date :

    2003-01-01




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English




    Easy-to-Apply Solution to a Persistent Safety Problem: Clearance Time for Railroad-Preempted Traffic Signals

    Long, G. / National Research Council | British Library Conference Proceedings | 2003



    Track Clearance Performance Measures for Railroad-Preempted Intersections

    Brennan, Thomas M. / Day, Christopher M. / Sturdevant, James R. et al. | Transportation Research Record | 2010


    Performance Measures for Railroad-Preempted Intersections

    Ernst, Joseph M | Online Contents | 2009