Optimizing the Location of U-Turn Median Openings at Signalized Intersections with Multitype Vehicles

Abstract

The location of a U-turn median opening has an important effect on traffic flow operations for a shared left-turn and U-turn (SLU) lane with traffic signals. It is the first thing to analyze the influences of the arrival modes of multitype vehicles on the traffic delay for an SLU lane. Two models are then formulated to calculate the loss time for the phase used by the concurrent left-turns and U-turns and that used by the concurrent through and U-turns. To seek the optimal location of a U-turn median opening, a single-objective optimization model is developed on the basis of the SLU lane capacity. Six experiments that consider three levels of traffic demand and whether the U-turning volume has an effect on the green splits and the optimal U-turn location are carried out. The results reveal that the optimal location of a U-turn median opening depends on traffic demand and composition, and such a location will approach the stop line if the arrival rate of multitype vehicles decreases or the proportion of U-turn vehicles increases.