Comparison of intersection and mid-block left turn collisions in the United States

Introduction: Left turning vehicles are involved in approximately 20% of motor vehicle collisions each year. Most of these collisions occur at uncontrolled intersections or mid-block areas that do not provide a protective left turn movement. Objectives: To evaluate the factors that might influence an occupant's injury severity during a left turn movement. Methods: We used the National Automotive Sampling System Crashworthiness Data System (1995-2005) to compare crash characteristics and injury outcome between intersection and midblock left turn collisions. Results: Total of 7,396 collisions were evaluated. Traffic control devices were present in 82% of intersection and 10% of mid-block collisions. After adjustment for potential confounding variables, drivers' injury severity was not significantly associated with the crash location. However, front seat passengers in mid-block collisions had 72% higher odds of experiencing an injury with injury severity score ≥ 9 (odds ratio: 1.72, 95% confidence interval: 1.09-2.69). Our analysis did not show that drivers or passengers in larger vehicles, e.g. sport utility vehicles and mini-vans, were at lower risk of more severe injuries in comparison to the car occupants in sedans. Conclusion: Road management strategies that restrict mid-block left turn movements on roadways with high speed limits might alleviate the magnitude of the problem attributed to left turn collisions. Installation of traffic controls signals or signs that notify the opposite traffic of the possible presence of mid-block left turning vehicles might be strategies that deserve more attention.