Bicycle Crossing Design and Signal Control Optimization for the Symmetric Intersection

The symmetric intersection (SI) is a type of unconventional intersection that could increase capacity of the intersection. Although this type of intersection is promising, the bicycle crossing method has not been designed for SI, which prevents it from implementation. In this study, we propose three bicycle crossing designs for the purpose of eliminating the conflict between bicycles and vehicles, and optimize the corresponding signal timing. The first is to reverse the bicycle lane on the right-hand-traffic arterial, so that left-turning bicycles can pass at any time, which can reduce the flow of bicycles through the conflicting area of the intersection. The second is to use an advanced stop line, which moves the stop line backwards and sets up a bicycle waiting area in the front to reduce the conflict between bicycles and vehicles. The third is to set up an exclusive phase for bicycles to separate vehicles and bicycles. A linear programming model that maximizes the capacity of the intersection for vehicles considering constraints such as signal phase and cycle duration is established to calculate the signal timing. A case study is performed to determine the optimal signal timing of each condition. The results show that the scheme of advanced stop lines could reduce delays and increase capacity of the intersection for bicycles, but the capacity for vehicles is reduced, and thus should be used when the traffic demand of motor vehicles is not high. In the condition of high-throughput vehicles, the exclusive phase for bicycles perform better.