抄録
Public transit systems have been a promising solution for the congestion and environmental problems of most urban areas around the world. Because it can reduce the negative effects of traffic jams and pollution caused by private vehicles, public transit systems have played an important role in development of sustainable environment in urban areas. Although public transit systems can reduce external cost efficiently, the externality of public transit system has not been sufficiently included in the existing models for public transit planning. This study aims to analyze optimal headway and length for the public transit system (i.e., urban rail) in a transportation corridor under the consideration of externality. A minimum total system cost objective is developed in a mathematical model considering insensitive and many-to-one demand pattern. The total system cost is composed of the operator costs, the user costs, and the external cost. The operator cost includes train operation costs, terminal operation costs, and terminal construction costs. The user cost includes the wait cost, the access lost and the in-vehicle cost. The external cost, which is evaluated according to the Green GNP account, includes fuel consumption cost, air pollution cost, and accident lost. A numerical example is given to demonstrate the applicability of the mathematical model developed. It is shown that under the consideration of externality, both the optimal length and the optimal headway should be longer than those generated by the conventional modeling process in which the externality is ignored. However, it is also shown that in some situations the optimal solutions have no significant differences, whether considering the externality or not.
