Turner-Fairbank Highway Research Center

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Safety Evaluation of Center Two-Way Left-Turn Lanes on Two-Lane Roads

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Technical Summary






This document is a technical summary of the Federal Highway Administration report, "Safety Evaluation of Center Two-Way Left-Turn Lanes on Two-Lane Roads." The objective of this study was to evaluate the safety effectiveness of installing Two-Way Left-Turn Lanes (TWLTLs) on rural roads as measured by crash frequency before and after the installation of the TWLTLs. The study also examined the effects of this strategy on specific crash types; total, injury, and rear-end crashes were examined in a rigorous analysis, while a cursory analysis was performed for head-on, intersection, and nonintersection crashes. The results of the analysis indicate statistically significant reductions at the 95% confidence level in total, injury, and rear-end crashes for the combined results of the four states examined. Further results are discussed in this TechBrief.

Link To Technical Summary

Safety Evaluation of Center Two-Way Left-Turn Lanes on Two-Lane Roads


highway safety
two way left turn lanes
two lane highways
highway design
rear end collisions
head on collisions
before and after studies
evaluation and assessment

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HSIS Summaries

HSIS Summary Reports are two to eight pages in length and include a brief description of the issue addressed, data used, methodology applied, significant results, and practical implications.

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Research Reports

A variety of research studies have been performed using data from HSIS. Many of the final reports prepared are now available electronically.

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Technical Summaries

Research reports are often summarized in executive summaries, technical briefs, or other abbreviated formats. Included here are those road safety summaries that involved research using HSIS data.

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Safety Analysis Tools

In addition to conducting research, HSIS resources are also used to develop products that can be used by practitioners in the analysis of safety problems.

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HSIS data are sometimes used in research studies that result in other types of finished products, such as dissertations, theses, and conference proceedings.

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