ROAD DESIGN: J-turns reduce crashes in Missouri study

The U of Mo. study found J-turn design resulted in a 34.8% reduction in crash frequency

Transportation Management News Columbia Daily Tribune, U of Mo. study December 27, 2013
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Researchers at the University of Missouri have found that the J-turn results in fewer accidents than a two-way stop at intersections of high-speed rural expressways and minor roads.

 

“Evaluation of J-turn Intersection Design Performance in Missouri” used field studies, a public survey, crash analysis and traffic conflict analysis. The field studies collected detailed video data at a J-turn site and a control site. The J-turn site was the intersection of U.S. 63 and Deer Park Road just south of Columbia. The control site was U.S. 63 and Calvert Hill Road, a two-way-stop intersection just north of Columbia.

 

The crash analysis included a before-and-after safety evaluation of five J-turn sites in Missouri. The J-turn design resulted in a 34.8% reduction in crash frequency for all crashes and a 53.7% reduction in crash frequency for all injury and fatal crashes.

 

None of the five sites exhibited a fatal crash following J-turn implementation. This five-site analysis showed that annual right-angle crashes decreased from 6.3 to 1.3, an 80% reduction. One of the most severe crash types, the left turn right angle crash, was completely eliminated by the J-turn, according to the study.

 

Public opinion about J-turns was mostly negative, according to the Columbia Daily Tribune. Sixty-two percent of the people surveyed said J-turns were not easy to navigate, and 60% disagreed that the J-turn made the intersection safer.

 

The researchers reported that some common concerns raised by survey respondents included difficulty in merging after the U-turn, improper use of acceleration and deceleration lanes, insufficient U-turn radius to accommodate large vehicles and driver confusion.

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