Minimization of Travel Time in Signalized Networks by Prohibiting Left Turns

The direct left turn at intersections increases delays and causes more accidents in certain conditions. Prohibiting left turns could increase the capacity of the road network and reduce the delays. This research aims to analyze which left turns should be prohibited in an urban road network to increase efficiency. Stochastic User Equilibrium (SUE), with left turn prohibition, is studied in this paper, by minimizing the travel time of the network. The left turn prohibition solution, the corresponding cycle time and green times are determined. A left turn prohibition filtering algorithm (LTPFA) is developed in this paper. The core of the algorithm is that the minor left turn flows have priority to be prohibited. The LTPFA succeeds to find optimal or near-optimal result of travel time in the shorter time compared with enumerating all left turn prohibition combinations. As the total traffic demands increase, the traffic network can benefit more from the left turn prohibition.