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.
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. 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.
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. DOTs, MPOs, and others to better estimate the change in transportation-related GHG emissions and energy use related to altered land use patterns.
The objectives of this research were 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.
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).
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).