Exploring Contributing Factors for Driver's Selection of Unconventional Outside Left-Turn Lanes

Abstract

A kind of special outside left-turn lane design has been increasingly used in urban areas in China recently. Unlike the traditional design, the special left-turn lane design locates the left-turn lane to the right of through lanes. The primary objective of this study is to evaluate the impacts of various factors such as traffic conditions, and the influence of geometric characteristics on driver's selection of outside left-turn lanes. Using traffic data collected from 10 particular approaches, a binary logic model was developed and found that the chance of a left-turning driver choosing the outside left-turn lane increases when the major-street traffic volume and the queuing length in inside left-turn lane increases; and decreases when the distance from the upstream side-street to the signalized intersection increases. Left-turning heavy vehicles and upstream side-street left-turning vehicles generally prefer outside leftturn lanes. Several guidelines were made to help designers in determining whether an outside left-turn lane is needed.