Study Details

Study Title: Safety Evaluation of Installing Center Two-Way Left-Turn Lanes on Two-Lane Roads

Authors: Lyon et al.

Publication Date:JAN, 2008

Abstract: The Federal Highway Administration (FHWA) organized a Pooled Fund Study of 26 states to evaluate low cost safety strategies as part of its strategic highway safety effort. One of the strategies chosen to be evaluated for this study was the installation of center two-way left-turn lanes (TWLTLs) on two-lane roads. Geometric, traffic, and crash data were obtained for 78 sites (21.3 miles) in North Carolina, 10 sites (6.0 miles) in Illinois, 31 sites (6.8 miles) in California and 25 sites (13.2 miles) in Arkansas. Empirical Bayes methods were incorporated in a beforeafter analysis to determine the safety effectiveness of installing the two-way left-turn lanes. There was a statistically significant reduction in total and rear-end crashes in each of four States whose installations were evaluated. Rural installations were found to be more effective in reducing crashes than urban installations in each of the four States. The general conclusion of this research is that TWLTLs can be a cost-effective treatment for two-lane rural locations, especially those with a high frequency of rear-end collisions involving a lead vehicle desiring to make a left-turn.

Study Citation: Persaud, B., C. Lyon, K. Eccles, N. Lefler, D. Carter, and R. Amjadi. Safety Evaluation of Installing Center Two-Way Left-Turn Lanes on Two-Lane Roads. Federal Highway Administration, FHWA Report No. FHWA-HRT-08-042, December 2007.

Related Citations: Lyon, C., B. Persaud, N. Lefler, D. Carter, and K. Eccles. "Safety Evaluation of Installing Center Two-Way Left-Turn Lanes on Two-Lane Roads." TRB 87th Annual Meeting Compendium of Papers CD-ROM. Washington, D.C., 2008.

Study Report: Download the Study Report Document

CMFs Associated With This Study

Category: Roadway

Countermeasure: Install TWLTL (two-way left turn lane) on two lane road

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.77522.54 StarsAllAllNot SpecifiedAll
0.68631.44 StarsAllAllNot SpecifiedAll
0.87412.64 StarsAllAllNot SpecifiedAll
0.84315.74 StarsAllAllNot SpecifiedAll
0.79720.34 StarsAllAllNot SpecifiedAll
0.62937.14 StarsAllK,A,B,CNot SpecifiedAll
0.72527.54 StarsAllK,A,B,CNot SpecifiedAll
0.46953.14 StarsAllK,A,B,CNot SpecifiedAll
1.019-1.93 StarsAllK,A,B,CNot SpecifiedAll
0.73926.14 StarsAllK,A,B,CNot SpecifiedAll
0.50149.94 StarsRear endAllNot Specified
0.50649.44 StarsRear endAllNot SpecifiedAll
0.58424 StarsRear endAllNot SpecifiedAll
0.78321.74 StarsRear endAllNot SpecifiedAll
0.61338.74 StarsRear endAllNot SpecifiedAll
0.48851.24 StarsAllAllNot SpecifiedRural
0.9623.83 StarsAllAllNot SpecifiedUrban
0.49250.84 StarsAllAllNot SpecifiedRural
1.028-2.83 StarsAllAllNot SpecifiedUrban
0.83316.73 StarsAllAllNot SpecifiedRural
0.9069.43 StarsAllAllNot SpecifiedUrban
0.72727.34 StarsAllAllNot SpecifiedRural
1.05-53 StarsAllAllNot SpecifiedUrban