Citation

Hutton JM, Bauer KM, Fees CA, Smiley A. J. Saf. Res. 2015; 54: 5.e1.15.

Affiliation

Human Factors North, Inc., 174 Spadina Ave, Suite 202, Toronto, ON M5T 2C2, Canada. Electronic address: asmiley@hfn.ca.

Copyright

(Copyright © 2015, U.S. National Safety Council, Publisher Elsevier Publishing)

DOI

10.1016/j.jsr.2015.06.016

PMID

26403901

Abstract

INTRODUCTION: The Strategic Highway Research Program 2 (SHRP 2) Naturalistic Driving Study (NDS) data were used to evaluate gap acceptance behavior of drivers at left-turn lanes with negative, zero, or positive offsets ranging from -29ft to +6ft. The objectives of the study were to develop guidance for the design of offset left-turn lanes used as a safety countermeasure, and to provide insight regarding the use of the NDS data to future users.

METHOD: The study included 3350 gaps in opposing traffic evaluated by 145 NDS volunteer drivers and 275 non-NDS drivers at 14 two-way stop-controlled intersections and 44 signalized opposing left-turn pairs. Logistic regression was used to model the critical gap length for drivers as a function of offset, under conditions when their view was either blocked or not by an opposing left-turning driver.

RESULTS: The analysis found that the critical gap was longer at left-turn lanes with negative offsets than at those with zero or positive offsets, and was also longer when sight distance was blocked by an opposing left-turning vehicle. Sight distance was much more likely to be restricted by an opposing left-turning vehicle at negative-offset and drivers at those intersections were less likely to accept a gap when an opposing left-turn driver was present.

CONCLUSIONS: Longer gap lengths could potentially result in decreased operational efficiency of an intersection. In addition, drivers making left-turns at negative-offset left-turn lanes are, on average, more likely to leave the shortest amount of time between their turn and the arrival of the next opposing through-vehicle, which may present a potential safety concern. PRACTICAL APPLICATIONS: The findings provide guidance for highway designers considering using offset left-turn lanes as a crash countermeasure. This research also highlights the benefits and limitations of using the SHRP 2 NDS data to answer similar research questions.

Language: en