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Mid-America Transportation Center

NDOR Effect of Phase Countdown Timers on Safety and Efficiency of Operations at Signalized Intersections

Final Report
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Researchers

  • Principal Investigator: Anuj Sharma (asharma3@unl.edu 402-472-6391)
  • Co-Principal Investigator: Elizabeth Jones (ejones1@unl.edu (402) 554-3869)
  • Project Status
    Complete
    Sponsors & Partners
  • Nebraska Department of Roads
  • About this Project
    Brief Project Description & Background
    Discharge headway is the time that elapses between consecutive vehicles as they get discharged form a queue at signals, usually observed when the vehicles cross the stop line. When the green is initiated, the first vehicle’s headway is measured as the time elapsed from the start of green to the time the first and second vehicles crossing the curb line. Common practice is to measure the headways as the rear wheels of the reference vehicle cross the curb line. In earlier studies it was reported that the first waiting driver will usually take more time to react to the red-to-green change before releasing the brake and start accelerating. The following driver will also incur some reaction time, which will be shorter with every subsequent drive in the line since the reaction times overlap. Finally headways tend to level out to the minimum headway value. It is reported that this 'leveling off' begins with the fourth or fifth headway. Phase countdown timers may help reduce headway among vehicles at the front of the queue. The objective of this research is to evaluate the effects of countdown timers on safety, efficiency of operations at intersections.
    Research Objective
    The objective of this research is to evaluate the effects of countdown timers on safety, efficiency of operations at intersections.
    Potential Benefits
    The information gathered through this project could help traffic engineers use phase countdown timers to reduce delays while optimizing safety and efficiency at intersections.
    Abstract
    Signalized intersections are important nodal points in transportation networks and their efficiency of operation greatly influences the entire network performance. One of the basic characteristics for intersection operations is the manner in which vehicles depart, or discharge, from the intersection when a green indication is received. Discharge headway is one parameter that is used for such analysis of traffic discharge at signalized intersections. Discharge headway is the time that elapses between consecutive vehicles as they get discharged form a queue at signals, usually observed when the vehicles cross the stop line. When the green is initiated, the first vehicles headway is measured as the time elapsed from the start of green to the time the first and second vehicles crossing the curb line. Common practice is to measure the headways as the rear wheels of the reference vehicle cross the curb line. In earlier studies it was reported that the first waiting driver will usually take more time to react to the red-to-green change before releasing the brake and start accelerating. The following driver will also incur some reaction time, which will be shorter with every subsequent drive in the line since the reaction times overlap. Finally headways tend to level out to the minimum headway value. This generally occurs when vehicles have fully accelerated by the time they reach the curb line. It is reported that this 'leveling off' begins with the fourth or fifth headway. Countdown timers may help reduce headway among vehicles at te front of the queue. The objective of this research is to evaluate the effects of countdown timers on safety, efficiency of operations at intersections.
    Project Amount
    $ 131,168
    Modal Orientation
  • Intelligent Transportation Systems
  • Safety and Human Performance