Planning bus system operations has traditionally relied heavily on the acquired knowledge of bus system planners and has been one of the last areas of transportation planning to be computerised. There are a number of programs available to design the allocation of drivers and vehicles to a bus system, but the planning process still lacks a detailed capability to determine the desired headways and short lines based on the levels of demand for service. Conventional wisdom has held that the regional forecasting models, based on zonal-level analyses of trip generation, trip distribution, mode split, and assignment, are too aggregate and too coarse to permit them to be used to assist in such planning efforts. There is no question that these models are coarse and aggregate. However, this paper demonstrates that they are still sufficiently realistic and accurate to be used for bus route planning at a line-by-line level and that for large bus systems they may be much better suited to the planning issues involved than any other available methodology. Some specific requirements that the models must meet to be used in this manner are described. A procedure is detailed for producing bus system statistics from the standard planning models of the Urban Transportation Planning System (UTPS) and it is shown how this procedure can be used in conjunction with the UTPS procedures to undertake detailed long-range planning of a bus system. The capability of the procedure to produce data that accurately reflect the base year is shown to be considerably greater than that normally associated with aggregate travel-forecasting models. The capability of using the procedure to refine a long-range bus system is demonstrated in a case study from the Los Angeles area, and this shows that the procedure has the capability to provide clear indications of a variety of improvements to the efficiency of the planned bus network.
Abstract