Using the schedule-based approach, in which scheduled timetables are used to describe the movement of vehicles, a dynamic transit assignment model is formulated. Passengers are assumed to travel on a path with minimum generalized cost that consists of four components: in-vehicle time; waiting time; walking time; and a time penalty for each line change. A specially developed branch and bound algorithm is used to generate the time-dependent minimum path. The assignment procedure is conducted over a period in which both passenger demand and train headway are varying. This paper presents an overview of the research that has been carried out by the authors to develop the schedule-based transit assignment model, and offers perspectives for future research.
This paper describes the application of a capacity restraint trip assignment algorithm to a real, large-scale transit network and the validation of the results. Unlike the conventional frequency-based approach, the network formulation of the proposed model is dynamic and schedule-based. Transit vehicles are assumed to operate to a set of pre-determined schedules. Passengers are assumed to select paths based on a generalized cost hnction including in-vehicle and out-of-vehicle time and line change penalty. The time-varying passenger demand is loaded onto the network by a time increment simulation method, which ensures that the capacity restraint of each vehicle during passenger boarding is strictly observed. The optimal-path and path-loading algorithms are applied iteratively by the method of successive averages until the network converges to the predictive dynamic user equilibrium. The Hong Kong Mass Transit Railway network is used to validate the model results. The potential applications of the model are also discussed.
Passengers' Waiting TimeAs discussed above, the waiting and transfer times in most of the Information is affecting our life in significant ways. Transit planners have a dream that one day they can fully utilise all available information as the model input, and the planning tool is also able to provide valuable information for policy making. Transit operators also want to realise their dream such that in one day they can quickly decide the incident management strategy by providing passengers with the time-dependent route guidance information. Passengers also imagine that one day they are able to plot their route and print their itinerary with detailed in-vehicle/waiting/walking/ transferring time before they leave their home or office. All is dream in the past in view of the lack of information (such as the detailed time-dependent origin-destination (O-D) demand information), as well as the limitation of computation power. As such, the conventional transit models often simplify the real situation or ignore some of the system/passenger behavior. With the advent of the information age, the introduction of a new transit modeling approach will make the dream comes true. This paper discusses the limitations of the conventional frequency-based static models and describes a new schedulebased dynamic model that was investigated by the authors. The challenges in developing the new model, as well as its limitations are also discussed. The new model is a user-friendly and powerful tool that can be operated satisfactorily on a personal computer and is capable of precisely and accurately modeling both system and passenger behaviors. As the output from the proposed model shows many detailed and accurate information, the model can be applied in many different areas.
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