Predicting Speeds in an Urban Right-Turn Lane

Right-turn lanes are used to provide space for the deceleration and storage of turning vehicles and to separate the turning vehicles from the through movement. When larger corner radii are used at the right turn, vehicles can turn at higher speeds (thereby minimizing speed differential between turning and through vehicles). A concern with the higher operating speed is the challenge it provides pedestrians. This project analyzed the impact of right-turn treatments on right-turn vehicles speeds at 19 urban approaches. Each approach had an exclusive right-turn lane that was separated from the through lane with either a lane line or a raised corner island. The 85th percentile free-flow speed near the middle of the right turn ranged from 20.9 to $33.8\mathrm{km}∕\mathrm{h}(13\text{–}21\mathrm{mi.}∕\mathrm{h})$ while on the approach it ranged from 27.4 to $46.7\mathrm{km}∕\mathrm{h}(17\text{–}29\mathrm{mi.}∕\mathrm{h})$ . Speed prediction equations were developed as part of this study.