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The National Academies

TCRP H-46 [Final]

Quantifying Transit’s Impact on GHG Emissions and Energy Use: The Land Use Component

  Project Data
Funds: $400,000
Research Agency: ICF Incorporated
Principal Investigator: Frank Gallivan
Effective Date: 10/11/2011
Completion Date: 12/1/2014

BACKGROUND

Higher density, mixed-use development and greater transit use can potentially contribute to reduced transportation-related greenhouse gas (GHG) emissions and energy use by facilitating shorter and  fewer automobile trips and more non-motorized (i.e., walking and biking) trips. Transit may support compact land use by reducing the need for parking and roadway vehicle capacity, enabling clustered development, encouraging bicycle and pedestrian travel, facilitating trip chaining, and reducing household automobile ownership. The characteristics and magnitude of the interaction between transit and land use and the resulting changes in transportation-related GHG emissions and energy use may occur in different ways. For example, public transportation investments may precede land development and the resulting patterns of land use may have lower GHG emissions and energy use. This is the case with many rail expansions. Land use changes and public transportation investments may also occur interactively or synergistically and mutually reinforce each other. This research seeks to better understand both cases, and consequently has two objectives: first, to estimate the direct impact of transit on land use and the associated impacts on GHG emissions and energy use (such as the case of a project expansion); and second, to understand the interactive or synergistic impact of changes in transit and land use on GHG emissions and energy use. These are described in more detail in the Objectives section below. The American Public Transportation Association (APTA) has developed an approach for transit agencies to estimate the transportation-related GHG emissions displaced or avoided in a region (see Quantifying Greenhouse Gas Emissions from Transit, APTA Standards Development Program, approved August 2009). The APTA approach takes into account GHG emissions from transit and the GHG reductions from (1) mode shift to transit, (2) congestion relief, and (3) compact development patterns and reduced travel by automobile resulting from improved transit services. The most challenging component of the APTA methodology is this final component—estimating the land use-related impacts of transit and the associated potential decreases in automobile travel on transportation-related GHG emissions.  A number of transit agencies have quantified the net impact of their services on transportation-related GHG emissions and energy use, including Chicago Regional Transportation Authority (Chicago RTA), Los Angeles County Metropolitan Transportation Authority (LACMTA), New York Metropolitan Transportation Authority (NY MTA), and Southeastern Pennsylvania Transportation Authority (SEPTA). While these transit agencies initiated their analysis subsequent to the APTA Standards Development referenced above, each adopted different approaches for measuring their transportation-related GHG emissions and energy impacts through land use. Although other transit agencies may seek this information, most lack sufficient resources to undertake similar analyses. Other significant research has been conducted on the linkage between transit, energy use, and GHG emissions. These studies have examined how the built environment affects vehicle miles traveled (VMT), GHG emissions, energy consumption, and other related topics. Examples of prior studies are included below in Special Note A.  A gap in the research to date has been assessing the specific role of transit as a driver in reducing transportation-related GHG emissions and energy use through its effect on land use at the transit system, corridor, and project levels. Another gap exists regarding how changes in land use and transit systems occur interactively or synergistically and mutually reinforce each other to reduce GHG emissions and energy use. As such, there is a need to review current research, develop a methodology to quantify the transportation-related GHG emissions and energy use related to land use that can be attributed to transit, and evaluate the synergistic interaction between transit and land use and its effect on GHG emissions and energy use. This research is particularly important since the land use component may be a significant factor for transit’s reduction of transportation-related GHG emissions and energy use. Transit agencies and other organizations are interested in measuring their net transportation-related GHG emissions and energy use for a variety of reasons. These include:
  • Understanding and measuring the full benefit transit provides to transportation-related GHG emissions and energy use through land use effects;
  • Measuring benefits of transit that historically have not been measured;
  • Compiling GHG inventories for climate registries;
  • Developing Climate Action Plans;
  • Complying with local legislation such as California’s SB 375;
  • Communicating with Metroploitan Planning Organizations (MPOs); and
  • Improving MPO modeling and estimation of transit benefits.
The results of this research are expected to assist transit agencies, state DOTs, MPOs, and others to better estimate the change in transportation-related GHG emissions and energy use related to altered land use patterns.
 

OBJECTIVES

The objectives of this research are to: (1) Develop a methodology to quantify the transportation-related GHG emissions and energy use related to land use changes that can be attributed to transit. The methodology developed shall quantify the impact of transit on land use and the resulting impact on transportation-related GHG emissions and energy use and shall determine what portion of land use related impacts, and thus changes in transportation-related GHG and energy use, are attributable to transit.
(2) Identify, describe, and, to the extent possible, quantify the synergistic interaction between transit and land use and the effects on transportation-related GHG emissions and energy use.

For both objectives, the research should: (1) enable analyses at the transit system, transit corridor, and transit project levels; (2) enable analyses of transportation-related GHG and energy use impacts for both current and future transit scenarios and the associated changes in land use; and (3) consider compatibility with the methodology presented in Quantifying Greenhouse Gas Emissions from Transit, APTA Standards Development Program, August 2009.

Because generally accepted standard methods already exist, this project will not develop methods to measure (a) GHG emissions produced by transit systems (e.g., emissions from bus fuel combustion, traction power, and transit facilities); nor (b) GHG emissions benefits and energy use impacts from mode shift and congestion reduction that can be attributed to transit services, as outlined in Quantifying Greenhouse Gas Emissions from Transit, APTA Standards Development Program, August 2009.
 

STATUS:
 The project's final report has been published as TCRP Report 176, Quantifying Transit’s Impact on GHG Emissions and Energy Use—The Land Use Component, and is available for download from the TRB Website along with the Land Use Benefit Calculator (an Excel file).


AVAILABLE PRODUCTS:

TCRP Report 176, Quantifying Transit’s Impact on GHG Emissions and Energy Use—The Land Use Component, is available for download from the TRB Website along with the Land Use Benefit Calculator (an Excel file).

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