When demand for transportation is low or sparse, traditional transit cannot provide efficient and good-quality service, due to its fixed structure. New transportation alternatives are therefore increasingly proposed, combining on-demand service adjustment capabilities to the regular route and schedule characteristics of traditional transit. Such so-called semi-flexible systems require careful planning, but no formalization of the corresponding decisions problems, nor any comprehensive methodology has been proposed yet. This paper aims at contributing to fill this gap by presenting a comprehensive literature review, and a general and unifying modeling framework for representing and planning semi-flexible systems. The latter takes the form of the Demand Adaptive Systems, which generalizes the semi-flexible systems described in the literature, and also offers a number of advanced features, the scheduling mechanism, in particular. The paper then provides a classification of planning decisions, which is used to structure a comprehensive and comparative literature review of the field of semi-flexible systems, including methodological contributions as well as a number of particularly significant practical experiences.

A survey on planning semi-flexible transit systems: Methodological issues and a unifying framework

Evaluation of flexible route bus transport for older people

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 flexroute 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.

Planning and Design of Flex-Route Transit Services

In this paper, to improve the reliability of flex-route transit service under uncertain travel demand, a meeting point strategy is proposed in which passengers can be picked up and dropped off either at their reserved stops or at meeting points that are within their acceptable walking distance. A two-stage optimization problem is introduced into the design of flex-route transit operations. Mixed integer programming (MIP) is employed to formulate the problem with a twofold objective: to serve as many requests as possible and to minimize the total trip time of the accepted passengers. A memetic algorithm is adopted to solve the problem in a reasonable amount of time. Simulation experiments based on a real-life flex-route transit service are conducted to assess the benefits of introducing meeting points. The results demonstrate that meeting points can significantly reduce the rejection rate by up to 24% at the cost of walking an acceptable distance. We also find that reducing the passenger fare to compensate for the inconvenience of walking to meeting points constitutes a win–win strategy that benefits both passengers and transit operators.

The benefits of introducing meeting points into flex-route transit services

This study addresses the issue of Automatic Vehicle Location (AVL) applications in small and medium sized transit agencies. Small to medium transit agencies were contacted to determine their perception of their experience with AVL and the benefits it has provided. All contacted transit agencies that deployed an AVL system perceive great benefits of AVL, especially in the areas of improved efficiency of the system by permitting automated dispatch and scheduling, improved customer services and communication, more efficient use of resources and improved on-time performance. In addition a survey was conducted of transit users in a Wisconsin community to assess the level of importance that they place on features of transit service which AVL can affect. The transit riders consider on-time performance and having real-time information as the most important factors in transit service. A framework for conducting benefit cost analysis is also provided based on data from the City of Racine, Wisconsin and some assumptions. It was found that consistent with cost benefit analysis of highway investment, AVL benefits largely occur to transit users if their waiting time can be reduced by even a small amount. AVL systems for small transit agencies also have the potential of sharing the system with other government agencies, such as public works departments, law enforcement agencies and other transit agencies.

Evaluation of the benefits of automated vehicle location systems for small and medium sized transit agencies

Information about the Potomac and Rappahannock Transportation Commission operational test is presented. The test focuses on service planning for the local flex-route transit services and the flag-stop commuter-rail feeder services, as well as their start-ups. Although the intelligent transportation system (ITS) operational test involves the application of automated vehicle location and real-time order-taking, scheduling, and dispatching of software, the planning and start-up operations of the non-ITS-enhanced phase of the flex-route and feeder services are addressed.

Randall G. Farwell

Papers

Planning, Implementation, and Evaluation of OmniRide Demand-Driven Transit Operations: Feeder and Flex-Route Services