Cellular automaton simulation of vehicles in the contraflow left-turn lane at signalised intersections

To improve the capacity of signalised intersections for left-turn vehicles, an unconventional left-turn design named the contraflow left-turn lane is applied at intersections in several cities of China. The main concept of the design is to provide more capacity for left-turn vehicles by dynamically making use of the adjacent opposite lanes. In this study, a cellular automaton model that simulates left-turn traffic flow at a signalised intersection with a contraflow left-turn lane was developed and verified by field data. Rules for vehicles entering the contraflow left-turn lane were proposed, and various factors including the vehicle type, driver type, and the ratio of U-turn vehicles were considered. The simulation results showed that the contraflow left-turn lane could increase the capacity of the intersection and decrease the delay of left-turn vehicles. Also, the optimal match between the length of the contraflow left-turn lane and the duration of the pre-signal green light can be evaluated via simulation. This study can provide a reference for the actual application of contraflow left-turn lanes.