A Metaheuristic Methodology for Feeder Bus Network Design Problem

The present paper deals with the transit network design problem related to the feeder bus lines defined as transit services for connecting suburban areas, where the demand has to be gathered, with the stops of the mass transit network, usually railway or underground stations. The objective of the research is the development of a procedure that simultaneously generates routes and frequencies of the feeder bus network in a actual-size large urban area. The solving procedure is articulated in 3 phases: in the first one, the study area is divided in several different basins, one for each main transit stop, on the base of some criteria like urban framework, main skeleton of the road network and pedestrian accessibility. In the second one, a heuristic algorithm generates two different and complementary sets of feasible routes, in order to provide a good balance between the maximization of the service coverage area and the minimization of the overall travel time. First set is composed by circular routes, generated solving a travelling salesman problem (TSP) connecting the highest demand node pairs in the area with the stop of main transit network. The second feasible set aims at developing feeder routes more direct than the others using the k-shortest path algorithm. The set of all feasible routes, generated taking into account only the main skeleton of the road network, is then the input data for the third phase where a GA is utilized for finding a sub-optimal set of routes with the associated frequencies. The proposed procedure has been implemented on a real-life size network, Rome, in order to compare its effectiveness with the performances of the existing transit network. The results of the application of the design procedure show that the feeder routes imply a more integrated transit network with a reduction of the total travel time, despite an increase of the number of transfers, in a more efficient way for the reduction of the operating costs and for an increase of the average load factor.