Evaluation and optimization of urban public transportation networks

So far, not much attention has been given to the problem of improving public transportation networks. In many cities these networks have been built sequentially and do not fit to the needs of the users any more. The results are long travel times and an unnecessarily high number of people who have to transfer. Compared to other investments for improving the service level of public transportation systems, the costs of rerouting the public vehicles are low and can, yet, highly improve the performance of the system.To evaluate a public transportation network, the shortest distance and the shortest route from node x to node y, taking the waiting times for a vehicle into account, must be known.It is shown in this paper, how to compute distances and routes efficiently for large networks. Using this algorithm it is described how to evaluate the average transportation cost of the passengers in a public transportation network.In the second part of the paper a heuristic algorithm is stated that improves a public transportation network using the average transportation cost as the objective.Finally, some experiences with real world problems are reported.