区域公交车辆调度问题的可靠性

Reliability of Regional Bus Scheduling Problem

为避免交通拥挤等突发事件干扰车辆正常、按时地完成某班次,从而造成公交车辆调度方案失效,需编制一个具较高可靠性的方案以适应环境变化.文中将区域公交车辆调度问题视为"部分班次被某车辆完成"的集合划分问题,假设不确定因素引起车辆延时完成某班次的时间服从正态分布,首次引入公交车辆调度方案的可靠度概念,考虑站场容量等约束因素,研究一类以车辆使用费用最少为第一目标和公交车辆调度方案可靠度最大为第二目标的多目标规划问题;再用约束法将第二目标变为约束条件,使该问题转化为单目标规划问题,设计求解问题的改进遗传算法,根据问题特征定义染色体编码、适应度函数、产生初始种群的启发式算法、交叉和变异操作等;最后,通过一个算例验证了模型和算法的正确性及有效性.

As the emergencies such as traffic congestion may interfere with vehicles to complete a trip on time and may further result in the failure of relevant bus scheduling scheme, it is highly necessary to establish a high-relia- bility scheme which adapts to the traffic environment change. In this paper, based on the assumption that the delay time caused by uncertain factors follows the normal distribution and that the regional bus scheduling problem can be regarded as a set-partitioning problem of ＂part of trips are completed by a vehicle＂, the concept of reliability is introduced to formulate the regional bus scheduling scheme as a multi-objective programming problem with the mini- mum cost of vehicles as the previous objective and with the maximum reliability as the secondary objective. Then, the constraint method is used to convert the secondary objective into the corresponding constraint, which makes the model to be a single-objective programming problem. Moreover, an improved genetic algorithm, which redesigns a chromosome coding, a fitness function, a heuristic procedure for population initialization and the crossover/mutation operation according to the features of bus scheduling, is designed to solve the problem. An example is finally given to show the correctness and effectiveness of the proposed model and algorithm.