Institute of Transportation, MOTC

       Temporary bus network adjustment problem is an important issue in planning and operation of bus transport systems. When bus operation faces special events or activities, such as road closures during construction and traffic control measures for special activities, some road sections are affected and some original bus routes may not be able to provide services again. Planners need to adjust the bus network in advance, and announce the adjusted bus routes to people. After the events or activities come to an end, the bus  etwork will be restored to its original state. The bus network adjustment is to reduce the business impacts of operators, and maintain the original service levels of passengers. However, some past practices were often used based on their subjective experiences, which lacks a systematic planning standard and fails to consider the relationship of before-and-after adjustment, as well as the impacts on existing passengers, often resulting in the waste of resources and loss of existing passengers.
       Hence, the study proposes a multi-objective mixed integer linear programming model with two conflicting objectives, which maximizes the bus network similarity and minimizes the normalized travel time, so as to consider both the change of bus network and the influence on existing passengers. In addition, the model is reformulated as a set-partitioning problem to increase the efficiency of problem solving. Also, augmented ε-constraint method is used to solve for Pareto optimal solutions, which can improve the problems of past studies like the inconsistency of different objectives, the presume of weights, and the evaluation of trade-offs between different objectives. To evaluate the effectiveness of bus network adjustment, the study verifies the reasonability and effectiveness of the model by test examples. Also, through scenario analysis, the impacts of different closed road sections and different number of bus routes are discussed. The results show that the proposed model is reasonable and effective. Also, decision-makers can have the most satisfactory adjustment plan based on their trade-offs between different objectives. The results of study can provide a reference for planners in making temporary bus network adjustment.