This paper reports on the culmination of a two year project to facilitate “smart growth” planning in the Las Vegas, Nevada metropolitan area. Using a group model building process, representatives of key municipal entities and resource management agencies developed a model for examining the potential effects of changes in land use and transportation planning on air quality, traffic congestion, and other quality of life factors. The model and the process both contributed significantly to broadening systems thinking capacity in regional planning. The model supports system-based policy evaluation and the process created a common systems language among the more than 20 land use, transportation, and air quality planners in the group. The model represents regional links between population, transportation infrastructure, land use characteristics, and air pollution. Model analysis shows that the most powerful tool for achieving policy objectives is a combination of land use design and transportation infrastructure that reduces the average number of trips per day and distance per trip. This paper describes the model, results of the analysis, and effects of the group model building process on the participants.