Effects of Transportation and Land Use Policies on Air Quality

Abstract

The effects of land use and transportation policies on emissions, ozone concentrations, and a metric for population exposure were investigated for Austin, Texas. Three distinct transportation and land use scenarios were examined with a gravity-based land use model and a standard travel demand model: a business-as-usual scenario, a road pricing policy that included a flat-rate carbon-based tax and congestion pricing of all Austin-area freeways, and an urban growth boundary policy. Two scenarios, a business-as-usual scenario and a flat-rate carbon-based tax and congestion pricing policy, were also examined with a novel, parcel-level land use change and land use intensity model and a standard travel demand model. Transportation and land use policies were predicted to have substantial effects on travel and on emissions of ozone precursors. Emissions of ozone precursors decreased markedly for all 2030 scenarios because of the implementation of more stringent federal motor vehicle emission control programs. Transportation and land use policies were predicted to lead to greater reductions of emissions of ozone precursors relative to the business-as-usual scenario. The effects of such policies on ozone concentrations and population exposure vary. Lower exposure was predicted for the road pricing scenarios, but a penalty appeared to exist in the form of relatively higher exposure predicted for the urban growth boundary on some days. This analysis indicates the potential complexity of planning for urban growth and equity and the need for integrated modeling and policy evaluation efforts.