- Feeder transit services perform the crucial first/last mile access to transit by connecting people within a residential area to a major transit network. In this paper, we address the optimal zone design problem faced by planners for feeder transit services with high demands and long length of service area, where a two-vehicle operation is assumed to be adopted in each zone. By balancing customer service quality and operating cost, we develop an analytical model of the system by assuming continuous approximations. Closed-form expressions and numerical procedures are employed to derive the optimal number of zones to aid decision makers in determining the best design as a function of the main parameters. Analytical expressions and results are then validated by simulation analysis. 2011 Springer-Verlag.