This paper develops a model for determining the sufficient number of stations for alterna tive fuel vehicles. The model extends a previous model to incorporate both ?ow demand and the trip length distribution, thereby providing a more appropriate framework for esti mating the sufficient number of stations. The service level is represented as the probability that the vehicle can make the repeated round trip between randomly selected origin and destination. The probability is obtained for the random pattern of stations for three cases:fuel is available at both origin and destination, fuel is available at either origin or destina tion, and fuel is available at neither origin nor destination. The analytical expressions for the probability demonstrate how the number of stations, the trip length, the vehicle range,and the refueling availability at origin and destination affect the service level of stations.The number of stations required to achieve a certain level of service is then calculated.