In light of time lag when using degree of saturation to judge traffic congestion in the intersection,the concept of critical saturation vehicle queuing length was proposed,the ratio of the vehicle queuing length of phase start time and critical saturation vehicle queuing length was defined as vehicle queuing congestion rate,and vehicle queuing congestion rate was used to judge the traffic congestion in the crossroads, developing a bus signal priority strategy for bus transit.Vissim software was used to simulate the bus signal priority strategy and testify its feasibility.The simulation results showed that in comparison with non-priority strategy,the implementation of bus signal priority strategy can remarkably decrease the average vehicle delay and average person delay for priority phase, and the average person delay for the whole phase cycle,only slightly increase the average vehicle delay and average person delay for non-priority phase,and rarely change the average vehicle delay for the whole phase cycle,which shows that it is feasible to use vehicle queuing congestion rate to judge the traffic congestion of all direction in the crossroads and to implement bus signal priority strategy in the case of traffic congestion.
