۱٫۱٫ Background and motivation

One of the most challenging problems in transportation planning is shifting a significant number of private car users to public transport (PT) in a sustainable manner. The problem of improving PT patronage and its compatibility with user needs is multifaceted. However, one may rather intuitively assume that improving PT service reliability, from the user perspective, and reducing operations costs from the perspective of PT operators will lead to an increase in ridership and competiveness compared with private car use. For most PT systems, inter-route or intermodal transfer connections are important factors affecting service reliability. Timetable synchronization is a useful strategy used to reduce passenger transfer waiting time, provide a well-connected service and improve PT service reliability (Ceder, 2001,2016). Most previous studies (e.g., Daganzo, 1990; Bookbinder and Desilets, 1992; and Ceder et al., 2001) on the PT timetable synchronization problem have treated the problem separately, rather than coupled with, or isolated from, other operation planning activities, such as vehicle scheduling, transit assignment and network design. However, as pointed out by Ceder (2001, 2016), it is preferable that all operation planning activities can be planned simultaneously in order to exploit the system’s capability to the greatest extent, and thereby, maximize its productivity and efficiency. Some researchers (e.g. Ceder and Stern, 1984; Van den Heuvel et al., 2008; Ibarra-Rojas et al., 2014; Liu and Ceder, 2016a; and Liu et al., 2017) have focused on integrating the PT timetable synchronization problem (TSP) with the vehicle scheduling problem (VSP) in order to analyze the tradeoff between level of service and operations costs. Various new mathematical programming models have been developed to serve as the basis for this tradeoff analysis for the integrated timetable synchronization and vehicle scheduling (ITSVS) problem. To date, there are two main decision-making problems that have not yet been addressed regarding an integrated approach to simultaneously analyze timetable synchronization and vehicle scheduling tasks. First, almost all previous studies focused on optimizing operation parameters only, such as trip offset times (departure time of the first trip), route headways and vehicle trip chains. However, the effect of the changes of these operation parameters on PT users’ trip choice behavior which have a heavy impact on other planning activities, is not taken into consideration in the timetable optimization process. Second, there is a lack of effective and efficient solution methods for finding a set of Pareto-efficient solutions so as to help for the purpose of assisting in multi-criteria decision analysis from the perspectives of both PT users and operators. To bridge these gaps, this study addresses the integrated PT timetable synchronization and vehicle scheduling problem with transit assignment (ITSVS-TA) for tactical and operational planning purposes.