The evolution of computer transportation modeling in montgomery county, maryland, over the past 15 years, is described in this paperalong with the ways in which transportation models have been used for planning and growth management. Transportation models have been used to link land development regulation decisions with the budget process for transportation infrastructure provision under the county'sadequate public facility ordinance, with level of service standardsfor acceptable traffic congestion levels used to set limits on new subdivision activity in parts of the county. Transportation models have been used to evaluate the long-range balance between current zoning and infrastructure projected under the master plan of highways. Build-out of current zoning with planned infrastructure leads to intolerable traffic congestion. By reducing the ratio between jobs and households, clustering employment, and providing a new light rail system connecting major centers of the emerging polycentric metropolitan region, with infrastructure to make the centers bicycle- and pedestrian-friendly, acceptable levels of traffic congestion could be achieved at much higher levels of urbanization. The development of transportation models to support these planning efforts, including calibration of a peak-hour factor model, a nested logit mode choice model sensitive to the quality of pedestrian access to public transportation, and subarea master planning model systems are discussed in this paper. It describes preliminary work in combining geographic information system (gis) technology with conventional regional transportation models. It describes how gis may be the best tool for dealing with transportaton behavior variables where the variance in the datawithin zones exceeds the variance between zones. This paper appearsin transportation research record no. 1262, Planning, management and economic analysis 1990.
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