A Simultaneous Bus Route Design and Frequency Setting Problem for Tin Shui Wai , Hong Kong

A bus network design problem for Tin Shui Wai, a su burban residential area in Hong Kong, is investigated, which considers the bus serv ic s from origins inside this suburban area to the destinations in the urban areas. The problem aims to improve the existing bus services by reducing the number of transfers and the total t ravel time of the users. This has been achieved by the proposed integrated solution method which can solve the route design and frequency setting problems simultaneously. In the p roposed solution method, a genetic algorithm, which tackles the route design problem, is hybridized with a neighborhood search heuristic, which tackles the frequency setting prob lem. A new solution representation scheme and specific genetic operators are developed so tha t the genetic algorithm can search all possible route structures, rather than selecting ro utes from the predefined set. To avoid premature convergence, a diversity control mechanis m is incorporated in the solution method based on a new definition of hamming distance. To i llustrate the robustness and quality of solutions obtained, computational experiments are p erformed based on 1000 perturbed demand matrices. The t-test results show that the d esign obtained by the proposed solution method is robust under demand uncertainty, and the design is better than both the current design and the design obtained by solving the route design problem and the frequency setting problem sequentially. Compared with the current bus network design, the proposed method can generate a design which can simultaneously redu ce the number of transfers and total travel time at least by 20.9% and 22.7% respectivel y. Numerical studies are also performed to illustrate the effectiveness of the diversity contr l mechanism introduced and the effect of weights for objective functions.