Operational and Safety Effects of Right-Turn Deceleration Lanes on Urban and Suburban Arterials

Right-turn deceleration lanes reduce the potential for rear-end collisions from vehicles slowing to make right-turn maneuvers. Right-turn lanes also improve arterial capacity by removing slower-moving vehicles from the main traffic stream. Transportation agencies must have an understanding of the traffic operational and safety effects of right-turn lanes to determine effectively where right-turn lanes are needed. Therefore, in this research, a computer simulation study of motor vehicles and pedestrians at right-turn lanes was conducted to determine their operational effects. A benefit-cost analysis of right-turn lanes that considered both their operational and safety effects was performed. The research indicates that right-turn maneuvers from a two-lane arterial at an unsignalized intersection or driveway can delay through traffic by 0 to 6 s per through vehicle where no right-turn lane is present. Delays to through traffic due to right turns in the same situation on a four-lane arterial are substantially lower, in the range from 0 to 1 s per through vehicle. Pedestrians at unsignalized intersections or driveways can have a substantial impact on delay to through vehicles due to slowing of right-turning vehicles yielding to pedestrians. Provision of a right-turn lane can reduce pedestrian-related delays to through traffic by as much as 6 s per through vehicle, depending on pedestrian volume. Also presented is an economic-analysis procedure that can identify unsignalized intersections and major driveways at which provision of right-turn lanes is cost-effective.