LINKED SIMULATION OF LAND-USE AND TRANSPORTATION SYSTEMS - DEVELOPMENTS AND EXPERIENCE IN THE PUGET SOUND REGION

Strategies to reduce motor vehicle travel by altering urban spatial st ructure are one piece of a comprehensive program to slow global warmin g. While the connections between urban spatial form and urban travel h ave long been recognized, there have been few attempts in the United S tates to model the interactions within the context of a public plannin g program in an urban region. One such effort, the Vision 2020 plan in the Seattle region, is described in this paper. The modeling tools ut ilized widely available travel and land-use models, applied interactiv ely. A wide range of variables, consisting of transportation facility investments, demand management measures and land-use controls, were gr ouped into identifiable long-term alternatives. The analysis suggested some ambiguity in the ability to model the processes, particularly wi thin a highly political planning program, and indicated rather modest effects of land-use changes on reducing urban travel over 20 to 30 yea rs. Land use and demand management were most effective when supported by significant investment in facilities, including transit. Although a ttempting to alter urban spatial structure may not be the most cost-ef fective place to seek reductions in vehicular emissions over this peri od of time, planning programs like Seattle's may be an opportunity to mold less travel-dependent urban regions for the next century.