Abstract: Passive bus signal priority (BSP) at isolated intersections is one important measure to reduce bus delay and improve bus service.Firstly,the relationship between cycle length and evaluation indices such as average vehicle delay and average passenger delay are studied,and the optimal cycle length calculating method is determined.Then a green split optimization method,which allocates marginal green time to signal phases according to the number of passengers,is brought forward to reduce average passenger delay.At last,one intersection with four critical phases is taken as example to evaluate the performance of the algorithm.Evaluation index of one phase BSP and multiple phases BSP algorithms are attained respectively and control benefits are compared with timing schemes without BSP.Results show that the number of priority phases has a strong influence on the performance.Average passenger delay can be reduced significantly when one or two phases are given priority.