The Société de Transport de la Communauté Urbaine de Montréal (STCUM; Montreal Urban Community Transit Corporation) has recently undertaken the task of computerizing its phone information center, called AUT-OBUS. AUT-OBUS provides callers with optimal route choices within the STCUM transit network. An original system based on geographic and operations data bases combined with interactive path calculation and data processing software has already been implemented. A special geographic information system was developed to process the origins and destinations on the basis of the client's specifications. Multiple forms of spatial referencing are provided: street addresses, trip generators and attractors, monuments, special activities, street intersections, transit references (subway and rail stations, bus routes, terminals, etc.). The best path calculation is carried out by using interactively calibrated impedance functions (walking, in-vehicle, waiting, transfers, fares, and mode restriction). An added challenge was the necessary consideration of the network geometry, commercial speed, day type, trip time, and headway and the validation of the computed paths with existing schedules. For a transit network the size of Montreal's, consisting of 16,000 bus stops, 230 bus routes, and a pedestrian network of 80,000 links and 28,000 nodes, the calculation of the optimal path for a given origin–destination pair is less than 2 sec with a typical personal computer with a Pentium processor.
