The impact of residential growth patterns on vehicle travel and pollutant emissions

In light of the increasing reliance on compact growth as a fundamental strategy for reducing vehicle emissions, it is important to better understand how land use-transportation interactions influence the production of mobile source emissions. To date, research findings have produced mixed conclusions as to whether compact development as a strategy for accommodating urban growth significantly reduces vehicle travel and, by extension, mitigates environmental impacts, particularly in the area of air quality. Using an integrated simulation approach coupled with long-term land development scenarios, we conducted an assessment of the impacts of different long-term primarily residential growth patterns on vehicle travel and pollutant emissions in the eight counties of the San~Joaquin Valley region in central California. The results suggest that higher residential densities result in slightly decreased regional vehicle travel and emissions. Our comparative analysis also suggests that the effects of future land use growth patterns may vary among different spatial areas. That is, compact growth strategies can result in significantly more travel and emissions changes in already fairly urbanized counties. This work indicates a minimum density threshold of approximately \num{1500} households per square mile is necessary to achieve commensurate emissions reductions relative to existing densities.