Quantifying Transit’s Impact on GHG Emissions and Energy Use—The Land Use Component (2015)

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51 S E C T I O N 7 The land use benefits quantified in this study can be used to estimate displaced emissions from transit for the purposes of a GHG inventory. APTA’s Recommended Practice for Quantifying Greenhouse Gas Emissions from Transit (2009) describes three categories of emissions displaced by transit and provides methodologies for their quantification: • Avoided car trips through mode shift from private automobiles to transit (referred to as the ridership effect in this research). • Congestion relief benefits through improved operating efficiency of private automobiles, including reduced idling and stop-and-go traffic. • The land use multiplier, through transit enabling denser land use patterns that promote shorter trips, walking and cycling, and reduced car use and ownership. The land use multiplier described in the APTA protocol is equivalent to the land use effect analyzed in this research in all but one aspect. The term “multiplier” was used in the APTA protocol because early estimation methods relied on stating the land use effects of transit in proportion to the ridership effects. For example, the APTA protocol recommends using a default national multiplier of 1.9 to estimate land use effects. This figure is multiplied by the total transit passenger miles traveled on a given transit system (with some adjustment for average occupan- cies of private vehicles traveling in the region). Table 1 of this report demonstrates that there is no consistent ratio of ridership benefits to land use benefits. For the regions included in Table 1, the ratio ranges from 1:1 to 7:1. There has also been a substantial conclusion about what exact parameter the “multiplier” should be multiplied by. Accordingly, the research team recommends using the term “land use effect” or “land use benefit of transit” going forward. 7.1 Applying the Land Use Benefit in a GHG Inventory The land use benefit of an existing transit system in terms of VMT, fuel use, and GHG emis- sions can be quantified using the calculator (available at www.TRB.org/main/blurbs/172110. aspx) produced as part of this research. Land use benefits are not proportional to ridership benefits, but rather are determined by two key variables: • Transit route density. • Transit revenue miles. (See Appendices A and B for a description of the statistical models used to isolate these variables.) The User Guide in Section 6 explains in detail how to quantify the land use benefit of existing transit by analyzing the benefits of the current transit system in the calculator. The sections that Recommended Practice for Quantifying GHG Emissions from Transit

52 Quantifying Transit’s Impact on GHG Emissions and Energy Use—The Land Use Component follow expand on that information with more specific detail about using the calculator for GHG quantification. 7.2 Quantifying the Land Use Benefit Using a Pre-Defined Region Most regions can obtain an estimate of the land use benefit of public transportation in their area by using the calculator’s pre-defined regions. It is not essential that the boundary of the pre-defined region (which corresponds to a federal-aid urbanized area) is an exact match for the boundary of the transit service area. Rather, it is most important that the two key variables described above (transit route density and transit revenue miles), as well as per capita VMT, are reasonably representative of the transit service area. Using a pre-defined region will provide a reasonable estimate of the per capita land use benefit in terms of VMT reduction under these circumstances. To calculate total regional effects in terms of gallons of gasoline saved and CO2e emissions reduced, users may want to supply their own values for the following: • Total regional population. Verify that the population size of the pre-defined region is a rea- sonable fit for the transit service area in order to ensure that the total benefits in terms of gasoline consumption and GHG emissions are accurately estimated. If the fit is not reason- able, apply the per capita VMT reduction estimated by the calculator to a user-provided population total. • Average fleet fuel economy (mpg). The calculator uses a single fuel economy assumption of 24.9 mpg for the national light-duty fleet, which is an average of the estimated on-road fleet fuel economy for 2013 to 2035, based on projections from the Department of Energy. Individual regions may want to customize this value using more specific data or projections. Users can apply the VMT per capita reduction from the calculator to custom values for these variables (total regional population and average fleet fuel economy) in their own calculations outside of the calculator. References to standard GHG emission factors are available in the APTA protocol. Transit agencies will note that the calculator quantifies the land use benefit of transit for an entire region, while many urban regions are served by more than one transit mode or provider. Regional land use patterns are a complex product of many historical factors, and transit agen- cies operating in the same region typically comprise an interdependent web of transit net- works rather than a series of independent ones. When a rail system is served by feeder buses from another transit agency, there is a combined land use effect of the two. In light of these complex interdependencies, the calculator itself does not quantify land use benefits for separate transit agencies. Transit agencies that wish to isolate the land use benefits of their service alone could do so in one of two ways: 1. If the transit agency truly operates independently in its own subregion within the pre-defined region included in the calculator, the land use benefits could be isolated by defining a custom region (see below and Section 6.1.3) limited to the transit service area. 2. If the transit agency operates within the same geography as other transit agencies, the regional land use benefits could be apportioned based on the agency’s share of total regional route miles or revenue miles. Using route miles would favor agencies with broader geographical coverage while using revenue miles would favor agencies with higher levels of service. Using an average of the two methods is recommended.

Recommended Practice for Quantifying GHG Emissions from Transit 53 7.3 Quantifying the Land Use Effect Using a Custom Region If no pre-defined region is a reasonable fit for the transit service area of interest, the user can define a custom region. Section 6.1.3 in the user guide provides more information about defining a custom region. Reasons to define a custom region include the following: • If the urbanized area most closely associated with your transit service area is not included in the calculator. • If the urbanized area that best aligns with the user’s transit service area is significantly smaller than the transit service area. If the transit service area covers multiple urbanized areas, the user should consider creating a custom region to include all relevant urbanized areas. • If the urbanized area that best aligns with the user’s transit service area is significantly larger than the transit service area. For megaregions such as New York and Los Angeles, a single urbanized area can encompass areas with dramatically different transportation and land use characteristics. In these cases, users may want to consider defining a custom area for the sub- region of the urbanized area served by their agency. Note that defining a custom region may require a substantial data collection effort.