Design lengths of left- or right-turn lanes with separate signal phases

Abstract

A study is described which applied a rational procedure to determine the design length for left-turn or right-turn lanes with separate signal control. For this type of intersection regulation, the arrival and service rate equations are reasonably accurate predictors for traffic operations of both left and right-turning lanes. The design criteria are applicable for those signalized intersections where special turning lanes are deemed to be warranted on one or more approaches. In any situation for turn lanes with separate-phase control, design tradeoffs between length of turning lane and ratio of green time to cycle length are readily achieved with the tabulated values. Any intersectional design should be guided by geometric and/or control warrants in terms of the necessities for special turning lanes and for separate signal phases that are applicable for these turning-lane lengths.