Assessing the Effects of a Dual-Service Left-Turn Phase

Dual-service left-turn phasing is often used to improve the performance of left-turn movements at certain geometrically constrained intersections. This paper examines the before and after performance of a dual-service left-turn signal timing plan through a field study at an existing signalized intersection with a short, dedicated left-turn bay. The dual-service left-turn signal timing plan adds an additional lagging left-turn phase to alleviate overflow and blockage conditions. High-resolution event-based data was collected to assess various performance measures such as green occupancy ratios, red occupancy ratios, and occupancy times of the left-turn movement for the dual-service left-turn signal timing plan and the lead/lead left-turn signal timing plan. The opposing thru movement was also analyzed using red occupancy ratios and occupancy times to determine the effects of the dual-service left-turn signal timing plan on the opposing thru movement. The field study concluded that implementing the dual-service left-turn signal timing plan reduced the red occupancy ratios and the occupancy times for the left-turn movement with the short, dedicated left-turn bay, resulting in an improvement in efficiency for the left-turn movement. The field study also concluded the implementation of the dual-service left-turn signal timing plan increased the number of large occupancy times for the opposing thru movement which suggests a decrease in efficiency of the opposing thru movement.

Language

  • English

Media Info

  • Media Type: Web
  • Features: Figures; References; Tables;
  • Pagination: 20p

Subject/Index Terms

Filing Info

  • Accession Number: 01764358
  • Record Type: Publication
  • Report/Paper Numbers: TRBAM-21-00683
  • Files: TRIS, TRB, ATRI
  • Created Date: Dec 23 2020 11:27AM