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

Abstract

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.

Relationship of Lane Width to Safety on Urban and Suburban Arterials

“…Lane width for both midblock segments and intersection approaches has been considered. A full report of the results of this research has been prepared by Potts et al (1).…”

Development of Left-Turn Lane Warrants for Unsignalized Intersections

“…A benefit-cost approach to justify right-turn deceleration lanes was presented by Potts et al (14). The benefits of the right-turn lane were determined for crash reduction (change in number of crashes) and delay reduction (improvements in arterial capacity from removing the slower-moving vehicles from the main traffic stream).…”

Methodology to Predict the Safety Performance of Urban and Suburban Arterials

“…The methodology presented above is suitable for predicting accident counts for roadway segments and intersections on urban and suburban arterials. Where observed accident history data are available, the predicted and observed accident counts can be combined using the Empirical Bayes (EB) method presented earlier in this report [see Equations (15) and (16)]. Special EB procedures apply for this HSM methodology because of the use of multiple base models with different over dispersion parameters; these special procedures are shown in Equations (17) to (25).…”