We deal with the headway which effects on the performance of the PRT(Personal Rapid Transit) system and the system safety. The headway, time between passage of one vehicle and the next, is one of the important factors to assess the line capacity, which has a cue to solve the problem of the congestion in public transportation. To decide the headway there are many important factors, especially such as the failure vehicle deceleration rate, the following simple analytical equation can be made to assess the relation between the line speed and the minimum headway. In this paper we employ a numerical analysis method using a simple analytical equations for the evaluation of the minimum headway and show simple simulation results.