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1 Transportation systems and land use patterns coexist in a complex and ever-evolving âecosystem.â Roads and transit systems are planned and constructed in order to serve homes and businesses, but new homes and businesses also locate where they will have access to existing or planned roads and transit systems. A growing body of research analyzes the extent to which public transportation systems beget land use changes in the form of more compact development. The evidence is mixed, but favors the theory that public transportation investments can, under the right circum- stances, promote more compact development. The TCRP Project H-46 research team calls this phenomenon the land use effect of transit (or simply the land use effect). (See Figure S1.) Compact development in turn provides a host of environmental and social benefits, includ- ing helping to reduce vehicle miles traveled (VMT), fuel use, and greenhouse gas (GHG) emissions. We call these benefits the land use benefits. Since land use effects lead to land use benefits, these terms are sometimes used interchangeably. The land use effect of transit is complementary to, but completely separate from, the rid- ership effect of transit (sometimes referred to as the direct effect of transit), whereby people ride buses and trains instead of driving private vehicles. The land use effect reduces the VMT of non-transit riders by fostering communities where trip distances are shorter and walking and cycling are more attractive options. There is evidence that the land use benefits of transit are often greater than the benefits generated by transit ridership. This study develops new methods to quantify land use effects and land use benefits using regionally specific inputs. Research Methodology The research conducted under TCRP Project H-46 is one of only a handful of research efforts to date to use statistical modeling techniques to determine the size of the land use effect. It is the only research effort to use multiple datasets to analyze and cross-validate the land use effect at multiple geographic scales. Most other research has started with assump- tions about the strength of the land use effect in order to quantify land use benefits. Statisti- cal modeling has the advantage of quantifying the magnitude of the land use effect itself, before quantifying land use benefits. In fact, the bulk of this research effort was devoted to analyzing the land use effect. Using statistical models allowed the research team to isolate particular transit variables that determine the magnitude of the land use effect in a region (such as transit supply and frequency), while controlling for other factors that are correlated with urban land use S u m m a r y Quantifying Transitâs Impact on GHG Emissions and Energy Useâ The Land Use Component
2 Quantifying Transitâs Impact on GHG Emissions and Energy useâThe Land use Component patterns (such as urban area population size and road supply). Two different datasets were used to conduct statistical analyses at different scales: ⢠The urbanized area dataset, which contains data at a macro scale on more than 300 federal-aid urbanized areas, with boundaries defined by the FHWA. ⢠The neighborhood dataset, which contains data at a micro scale for nine diverse regions in the United States: Austin, Texas; Boston, Massachusetts; Eugene, Oregon; Houston, Texas; Kansas City (Missouri and Kansas); Portland, Oregon; Sacramento, California; Salt Lake City, Utah; and Seattle, Washington (using Metropolitan Planning Organizationâdefined boundaries). Research Applicability This report contains research and findings that will be useful to ⢠Transit agencies. This research can help to quantify the benefits provided by their service and better understand the characteristics of transit service that contribute to more compact development. Land use benefits quantified in this research can be used as a regionally specific alternative to APTAâs national level land use multiplier. ⢠Planners. This research can help in considering the likely land use developments associated with planned transit service and key variables that affect development activity. ⢠Modelers. This research can inform elasticities used in land use models. ⢠Researchers. This research can inform future research on the relationship between transit service and land use patterns. Figure S1. The land use effect of transit.
Summary 3 Summary of Key Findings Key findings of the research include the following: ⢠Effect on population densities. Taking the entire U.S. urban population in aggregate, gross population densities would be lower by 27% without transit systems to support compact devel- opment. In other words, U.S. cities would consume 37% more land area in order to house their current populations. The land use effect of existing transit makes U.S. cities more compact. ⢠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% decrease in VMT, transportation fuel use, and transporta- tion 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%. This is a substantial change given that only 4% of passenger trips are currently made by transit in U.S. metropolitan areas. ⢠The land use benefit of transit. The land use benefit of transit varies across urban areas, rang- ing from a 1% to 21% 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.1 ⢠Adding a rail station to a neighborhood that did not previously have rail access is associated with a 9% 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% 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 improv- ing the bus and rail network in individual neighborhoods, can also have potent land use effects. ⢠An analysis of the Portland Westside light-rail extension found that the land use effect increased densities by 24% in the corridor area between 1994 and 2011. These changes corre- spond to a 6% household VMT reduction due to the land use effect and an additional 8% VMT reduction due to the ridership effect. Land Use Benefit Calculator The TCRP Project H-46 research team created the Land Use Benefit Calculator (âthe calculatorâ), an Excel-based sketch-modeling tool, to apply the research findings. The cal- culator (available at www.TRB.org/main/blurbs/172110.aspx) is designed to allow transit agencies, metropolitan planning organizations, and other interested parties to estimate the land use benefits of their existing or planned transit projects with a minimum amount of input data required. Specifically, the calculator allows the user to estimate the following: ⢠The land use benefits of the existing regional transit system. ⢠The land use benefits of a regional transit plan. 1 Complementary ridership effects of transit vary based solely on the level of transit ridership in individual regions.
4 Quantifying Transitâs Impact on GHG Emissions and Energy useâThe Land use Component ⢠The land use benefits of a new transit route or improved transit service along an existing corridor. ⢠The land use benefits of a new transit station or stop or improved transit service to an existing station or stop. All land use benefits are estimated in terms of the following metrics: ⢠VMT reduction. ⢠Gasoline consumption reduced. ⢠GHG emissions saved. Future Research The following future research on this topic would be useful: ⢠Different approaches to measuring density. Gross population densities, the primary mea- sure used in this research, have a clear relationship to travel patterns. But population-weighted densities may be a better predictor of travel patterns. Calculating population-weighted densi- ties for all urban regions will require a substantial data collection effort. ⢠Innovative approaches to accounting for the influence of real estate markets and public support on the land use effect. These are two of the most important factors in determining whether and how much development occurs around transit. Future research should quantify their impact. ⢠Research on methods to match appropriate transit vehicle capacities with current or expected land use patterns. While using higher capacity vehicles probably would not encour- age densification in and of itself, transit agencies would benefit from more information about the correlation between vehicle capacity and land use patterns.
