Citation

Pirinccioglu F, Lu JJ, Liu P, Sokolow G. Transp. Res. Rec. 2006; 1953: 172-179.

Copyright

(Copyright © 2006, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

This paper evaluated the safety effects of right turns followed by U-turns (RTUT) at signalized intersections and at unsignalized median openings as an alternative to direct left turns (DLT) from driveways or side streets on four-lane arterials. The safety of both alternatives was evaluated on the basis of traffic conflict analysis. Nine types of conflicts were used for this study. Five of the conflict types were related to RTUT movements, while the rest were related to DLT movements. More than 500 h of data were collected at 16 sites with the help of video recording equipment. Data collection sites were divided into two sets by geometric criteria. At the first set of sites, the drivers had to complete the U-turn movement of RTUT at a signalized intersection. In contrast, at the second set of sites, the U-turns were at unsignalized median openings. At signalized intersection sites, DLT movements generated two times as many conflicts per hour as RTUT movements. When the effects of traffic volumes were taken into consideration, RTUT movements had a 5% higher conflict rate than DLT movements. Severity comparison of DLT and RTUT movements indicated that RTUT-related conflicts were less severe than DLT-related conflicts. At unsignalized median opening sites, DLT movements generated 10% more conflicts per hour than RTUT movements. Furthermore, another conflict rate (conflicts per 1,000 vehicles involved), which takes the effect of traffic volumes into consideration, was 62% higher for DLT movements than for RTUT movements. Severity analysis results indicated that DLT movements had higher average severity scores than RTUT movements.