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Abstract for presentation (Poster or Podium)

Transportation Safety

Understanding Left-turning Vehicles’ Red Light Violations: Permissive-Protected vs Protected-Only

Sunday, June 16, 2024
1:15 PM - 2:30 PM ET
Room: Galleria
Abstract:

Improving safety at signalized intersections is one of the top priorities for U.S. transportation agencies, with red-light running (RLR) being a particularly dangerous issue. RLR often leads to severe right-angle, rear-end crashes, resulting in many fatalities and injuries. Left-turn phasing is a specific concern within this problem, as it involves conflict points that can lead to severe crashes such as right-angle and vehicle-to-pedestrian crashes. Left-turn phasing operates in various modes, including permissive, protected, protected-permissive, split phasing, and prohibited. Two primary left-turning phases, permissive-protected left turn (PPLT) and protected-only left turn (POLT), are common left-turn phasing modes. POLT is generally considered safer due to fewer conflict points with pedestrians, bicycles, and crossing vehicles. However, it may increase intersection delays, necessitating a balance between mobility and safety. This research in Phoenix aims to assess how intersection and corridor characteristics, such as traffic flow, signal timing parameters, speed limits, and number of lanes contribute to left turn RLR events while distinguishing between POLT and PPLT. The study’s findings could offer valuable insights to transportation engineers and agencies, helping them understand RLR patterns associated with left turn phasing modes.

Learning Objectives:

Attendees can expect to learn the following from this session:
  • Upon completion, participants will be able to analyze and recommend effective safety strategies and countermeasures to reduce red light violations for left-turning vehicles at signalized intersections.
  • Upon completion, participants will be able to interpret and assess left-turning driver compliance behavior at intersections, elucidating the factors influencing red light violations.
  • Upon completion, participants will be able to understand and compare different left-turn modes, including the advantages and disadvantages of protected-only and permissive-protected modes, to inform decisions to improve intersection safety.