NCHRP Report 524: Safety of U-Turns at Unsignalized Median Openings

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Abstract:

Potts, I. B., D. W. Harwood, D. J. Torbic, K. R. Richard, J. S. Gluck, H. S. Levinson, P. M. Garvey, R. S. Ghebrial, NCHRP Report 524: Safety of U-Turns at Unsignalized Median Openings, Transportation Research Board of the National Academies, Washington, D.C. (2004)

      This report presented the results of an investigation into how U-turns affect safety and operations at unsignalized median openings, specifically on urban and suburban arterials. The study included 918 unsignalized median opening on 62 different arterials in seven states.  In addition to analyzing the crash data at each of these locations, observational studies were conducted at over 100 sites and focused on driver behavior while making U-turns.  Based on the results of this research, there is no evidence to suggest that U-turn movements have significantly different crash rates than traditional left-turn movements.  In addition, for both urban and rural locations, mid-block median openings had lower crash rates than traditional three and four leg intersections for U-turns and left-turns combined.  One limitation of the study was the small sample size due to the fact that U-turns are a very rare maneuver compared to other turning movements.   It should also be noted that crash reports do not accurately differentiate between U-turns and left-turns, and thus much of the analysis required the two movements to be grouped together.

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