Safety Impacts of Right-Turn Lanes at Unsignalized Intersections and Driveways on Two-Lane Roadways: Crash Analysis

Safety benefits of right-turn lanes (RTLs) have typically been estimated on the premise that right-turn movements (RTMs) only lead to rear-end (RE) crashes, and RTLs completely eliminate such RE crashes. This premise is reexamined in this study. Five-year, event-specific, statewide, historical data of traffic crashes reported on Minnesota's two-lane trunk highways were analyzed using logistic regression models (LRMs) to determine the safety impacts of RTMs/RTLs at uncontrolled major road approaches to intersections/driveways. It was found that the crashes caused by right-turning vehicles were less severe (mostly property damage), and interestingly, only 39% of those were identified as RE type. Right-turn lanes were found to reduce such RE crashes, on average, by 30% (not completely eliminate), reduce crash injury severity, and decrease the associated economic costs by 26%. Relative risks of RE crashes at driveways were 1.3 to 1.9 times higher compared with those at intersections, suggesting the need for separate set of volume warrants for RTLs. Logistic regression models developed provide the relationships to quantify RTL benefits for different roadway/operating conditions found statewide and can serve as a basis for safety-based warrants.

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