Members of the Colorado/Wyoming Section of ITE conducted a study to examine the use of permissive double left turn phasing at signalized intersections (two adjacent left turn lanes proceeding while yielding to oncoming traffic). The purpse of the study was to determine if permissive double left turn movements experience reasonable accident rates, as compared with protected-only double left turns and with single left turns. Some potential problems with permissive double left turns are: sight distance, vehicle conflicts, and driver judgement. First, a literature search was conducted to locate previous work that has been done on this subject. Second, a survey was conducted of state DOTs and some local agencies to determine the extent of use of permissive double left turns, and to see what policies exist that address this type of signal operation. Third, data was collected at traffic signals in the Denver and Colorado Springs metropolitan areas to compare accident rates at signals with single and double left turns operating with permissive and protected-only phasing. Fourth, a delay study was conducted on a corridor in the Denver metropolitan area to determine the delay impacts of protected-only double left turn phasing as compared to protected/permissive operation.


  • English

Media Info

  • Features: Figures; References;
  • Pagination: p. 214-218

Subject/Index Terms

Filing Info

  • Accession Number: 00712611
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Oct 23 1995 12:00AM