Urban Form and the Demand for Travel
Because the transportation sector is such a sizeable contributor to total U.S. greenhouse gas emissions—33 per cent—reducing transportation emissions will be a primary objective for any comprehensive U.S. greenhouse gas mitigation policy. In order to achieve the long-term stabilization of CO2 and other greenhouse gas emissions from the transportation sector, few measures would have a greater impact than the reform of land-use practices prevailing in the United States. As the emissions maps make clear, there is a direct correlation between low CO2 emissions and the reductions in auto use that accompany transit-friendly neighborhoods with high residential densities. Neighborhoods with lower rates of auto use, themselves reflections of lower household auto ownership, are neighborhoods that generate fewer greenhouse gases. How we build cities, therefore, has atmospheric consequences.
Those consequences also have an economic impact on the budget of typical urban households. Households in higher density neighborhoods served by transit incur lower transportation expenses because they are freed of many the costs of auto ownership the second greatest expense for American households. Were this efficiency extended to a greater percentage of urban inhabitants, the wealth freed at the household level would be enormous, on the order of $2.8 billion in the city of Chicago alone. The lower levels of auto ownership that accompany high-density land uses lead to lower vehicle miles traveled (VMT [glossary] a measure of the total distance driven by automobiles in a given region), fewer greenhouse gases, and ultimately lower transportation expenses per household. Reduction of transportation sector CO2 from changes in land use is therefore an efficiency that has a measurable economic benefit.
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Early
Research on Travel Demand
Competition with the Automobile
Thresholds of Transit Effectiveness
Travel Demand and Location
Efficiency
Transit and
Suppressed Auto Trips