Development and Evaluation of the Dynamic Left Turn Intersection

Dual left turn lanes are typically operated with protected left turn signals, which means much extra delay during non-peak hours compared to permissive operation.  To reduce this delay, the authors designed, installed, and tested a “dynamic left turn intersection” (DLTi), which is a new way to operate dual left turn lanes.  With DLTi, the both lanes are operated with protected phasing during the peak hours when higher capacity is needed, and only the leftmost left turn lane remains open for protected-permissive operation during off-peak hours.  The authors devised a set of standard traffic control devices that are relatively inexpensive to install and can be operated with conventional signal control software.  After developing site selection criteria and choosing a test site, the authors were able to test for the DLTi benefits and compliance levels at that site.  The benefit looks to be substantial in terms of delay savings, with a pay-off of five months as operated by the Town at pre-Covid-19 demand levels.  The crash experience has been minimal, and the public comments received have been predominantly negative but not overwhelming.  Around 85 percent of left-turning motorists are complying when the rightmost left turn lane is closed—which means the authors have shifted the previous lane choice of almost 50 percent of drivers.  All things considered, the team believes that DLTi has been a success, that it should remain in place at the test site, and that the NCDOT and other agencies should begin searching for other suitable locations for DLTi installation.

• Record URL:
  https://annualmeeting.mytrb.org/OnlineProgram/Details/15565
• Supplemental Notes:
  • This paper was sponsored by TRB committee AKD80 Standing Committee on Roundabouts and other Intersection Design and Control Strategies.
• Corporate Authors:

  Transportation Research Board

  ,    
• Authors:
  • Hummer, Joseph E
  • Milazzo, Joseph S
  • Galloway, Jason
  • Spencer, David
  • Topp, Andrew
  • Chapman, Jeremy R
• Conference:
  • Transportation Research Board 100th Annual Meeting
  • Location: Washington DC, United States
  • Date: 2021-1-5 to 2021-1-29
• Date: 2021

Language

• English

Media Info

• Media Type: Web
• Features: Figures; References; Tables;
• Pagination: 16p

Subject/Index Terms

• TRT Terms: Evaluation; Intersections; Left turn lanes; Left turns; Traffic control devices
• Identifier Terms: North Carolina Department of Transportation
• Geographic Terms: North Carolina
• Subject Areas: Highways; Operations and Traffic Management;

Filing Info

• Accession Number: 01763830
• Record Type: Publication
• Report/Paper Numbers: TRBAM-21-01537
• Files: TRIS, TRB, ATRI
• Created Date: Feb 4 2021 10:57AM