Citation

Shebeeb O. ITE J. 1995; 65(7): 52.

Copyright

(Copyright © 1995, Institute of Transportation Engineers)

DOI

unavailable

PMID

unavailable

Abstract

This article describes a study that was conducted to evaluate safety and efficiency of left-turn movements at signalized intersections. The purpose of the study was to develop models that capture potential trade-offs between left-turn efficiency and safety. Researchers performed statistical and traffic engineering analyses of actual field data, concentrating on accident and left-turn delay data for various left-turn phasing treatments. The phasing treatments studied included: 1) permissive only, 2) lead-protected only, 3) lag-protected only, 4) lead-protected permissive, 5) lag-protected permissive, 6) lead Dallas, and 7) lag Dallas. Investigators found that protected-only phasing offers the highest level of safety, but are least efficient, and permissive-only treatments offer the highest efficiency/lowest safety. No significant difference was noted between lead and lag in left-turn sequences. The author concludes that from an operational point of view, traffic engineers should always favor the permissive over the protected phasing. This research allows the development of analytical models that assess the magnitude of trade-offs between safety and efficiency.