Bi-level Optimization Method for Urban Public Transport Regional Dispatching

To optimize regional bus scheduling, a bi-level model, in which the upper goal was waiting time and the lower goal was fleet size, was constructed. However, obtaining the optimal solution of the model was difficult because of the interaction between the upper and lower targets. Therefore, an algorithm was introduced that transformed the lower level target into the constraints of the model to achieve a simple solution. For the given value of fleet size, a fleet size search algorithm was proposed based on a deficit function. Furthermore, to establish the constraints of fleet size, three types of time points were put forward, and logical variables were introduced to represent the selection of departure scheme. By constraining the value of the deficit function corresponding to the accounting time point, the current departure scheme can meet the requirements of the established fleet size. On the basis of the determination of the fleet size and the constraints, the best departure scheme can be obtained by solving the model. To verify the feasibility of the model, bus lines in Harbin were taken as an example. The best transfer time scheme was found to reduce the range of waiting time by 10.3% compared with that of the initial scheme, and the best fleet size scheme was found to reduce the range of initial fleet size by 15.2%. The model calculation results provide alternatives for bus operation enterprises at the boundary of the scheme, enabling bus operators to select the best departure scheme by combining the expected operation objectives and the actual bus scale, thereby improving the actual operation level. © 2021, Editorial Department of China Journal of Highway and Transport. All right reserved.