Reliability Based Public Transit Schedule Optimization

With the continuous development of urban economy and society and the increase of urban traffic volume, traffic problems. People gradually realize that it is important of developing Public Transit (PT) to solve urban traffic problems. PT operation management has played a decisive role in service quality. The bus passengers’and bus companies’time, money and other loss caused by the uncertainty of the running time can be effectively reduced through improving the reliability of the transit operation level. Therefore, it is necessary to further research the bus scheduling theory and its reliability problem.Bus schedule design is the one absolutely necessary process of Public Transit Planning and Operation. Cost and reliability are main measures considered in transit schedule design. The transit schedule parameters’effect on the reliability and schedule-based holding control strategy are firstly studied. Schedule-based holding control strategy is an easy measure to improve service reliability, which is a strategy in which a bus arriving early at a time point should hold until its scheduled departure time, which. However, the holding control can only correct early arrival of the bus. To help a late bus to gain in the schedule, some slack time has to be built in the schedule to provide time redundancy and to absorb travel time randomness. The shorter headway can also improve the reliability of waiting time. Through the analysis of the headway and the holding strategy’s effect on the reliability, the model of service time’s reliability, which controls the public transit lines under the holding strategy, is developed. The study finds that holding control strategy can improve the reliability of the transit, but the holding strategy should be optimal with scientific methods.In addition, how many time points and where to locate also affect the holding control strategy and thus the cost-effectiveness of the schedule. This special schedule design problem is investigated in this research by the use of both cost analytical and mathematic optimal methods. Optimal or near-optimal schedules can be found by minimizing the total cost associated with the schedule, which includes the passenger waiting time cost, delay cost to through passengers, delay/early penalty and operating cost. Considering the characteristics of the scheduling model, the heuristic algorithm is used to solve the model. The cross over and mutation technique is improved to satisfy the model, and the advanced technique could avoid being trapped in local optima.Synthesize Considering the models of service time’s reliability and of systemcost, proceeding from the realities of planning and strategic decision, bi-level planning model of transit operation based on the reliability is developed, which considers the lower target-minimum cost and constraint, consistent with the upper overall goal-maximum reliability, and includes headway and scheduling strategy variables. All those make every effort to optimize the transit operation design in system. It also designs an adjusting algorithm and case to solve the verification. It is shown that the optimal schedule is sensitive to demand pattern along the route, and desirable locations of time points are stops where the number of passengers is predominant to others. But demand is not the solo factor to consider. According to optimizing the headway and scheduling strategy, both of reliability and cost become better in the system.