Planning and design of flex-route transit services

A theoretical investigation is presented of various issues involved in the planning and design of flex-route transit services. An analytical model is proposed for an idealized operating environment with the objective of determining the optimal slack time that should be allocated to a flex-route segment. The optimization objective is defined to minimize total operator and user cost, which enables a systematic examination of complex interactions among the system parameters. An equation is derived for the relationship between the number of feasible deviations and various system parameters such as slack time, zone size, and dwell time. Subsequent analysis shows that the analytical model is elaborate enough to provide substantial insights into various issues that may arise in designing a flex-route service. A simulation analysis is conducted to validate some of the conclusions drawn from the analytical model and to further analyze the implications of stochastic variation in passenger demand.