Quality Public Transit Benefits Land Use Outcomes

A new report, "Quantifying Transit’s Impact on GHG Emissions and Energy Use—The Land Use Component," by the Transit Cooperative Research Program, uses sophisticated statistical analysis to examine interrelationships between transit and land use patterns to understand their impacts on urban development patterns, per capita vehicle travel and pollution emissions. It includes a calculator tool that planners can use to predict these impacts in a particular situation.

This research found:

• Effect on population densities. U.S. urban population densities would be 27 percent lower without transit systems to support compact development, causing these cities to consume 37 percent more land area in order to house their current populations. 

• Effect on VMT, fuel use, and transportation GHG. By providing more walking and biking opportunities and making some journeys by car shorter, the land use effect of transit produces land use benefits: an aggregate 8 percent decrease in VMT, transportation fuel use, and transportation GHG emissions in U.S. cities.

• Effect of transit trips replacing automobile trips. By transporting people on buses and trains who would otherwise travel by automobile, transit systems also produce a complementary ridership effect. In aggregate across U.S. cities, transit ridership reduces VMT, transportation fuel use, and transportation GHG emissions by 2 percent. This is a substantial change given that only 4 percent of passenger trips are currently made by transit in U.S. metropolitan areas.

• Land use benefit of transit. The land use benefit of transit varies across urban areas, ranging from a 1 percent to 21 percent reduction in VMT, transportation fuel use, and transportation GHG emissions compared to a hypothetical scenario without transit. Urban areas with higher route densities of transit, service frequencies of transit, and availability of light rail have higher land use benefits. Not surprisingly, higher land use benefits of transit are generally found in more densely developed areas.

• The land use effect of transit in a given region typically reduces GHG emissions more than the ridership effect. The average ratio of land use benefits to ridership benefits across all U.S. cities is 4:1, but the ratio varies substantially across different urban areas.

• Adding a rail station to a neighborhood that did not previously have rail access is associated with a 9 percent increase in activity density (combined population and employment density) within a 1-mile radius of the rail station. The corresponding land use benefit is a 2 percent reduction in VMT (for households within the 1-mile radius), transportation fuel use, and transportation GHG emissions.

• Improving employment accessibility, by clustering new jobs around transit nodes or improving the bus and rail network in individual neighborhoods, can also have potent land use effects.

• Analysis of Portland’s Westside light-rail extension found that the land use effect increased densities by 24 percent in the corridor area between 1994 and 2011. These changes correspond to a 6 percent household VMT reduction due to the land use effect and an additional 8 percent VMT reduction due to the ridership effect.

This is a major contribution toward planners understanding of how transportation planning decisions affect land use development patterns, and how this leverages changes in travel activity, energy consumption and pollution emissions.