- Although state departments of transportation and metropolitan planning organizations have a vital role in reducing greenhouse gas emissions from transportation sources, the U.S. Government Accountability Office found inconsistent approaches on whether and how these agencies measure on-road vehicle GHG emissions.
- In a report issued Thursday, the GAO found “a few examples among the selected state DOTs and MPOs that have targets for reducing on-road greenhouse gas emissions.”
- Although most of the state DOTs and MPOs that GAO interviewed “agreed that calculating emissions is not all that difficult,” GAO Director of Physical Infrastructure Elizabeth Repko said on a Thursday podcast that some faced challenges related to staffing, availability of data and quantifying the results of investments to reduce emissions.
Transportation is the largest source of greenhouse gas emissions in the U.S., responsible for 29% of all sources in 2021. According to the GAO, the nation’s 4 million miles of roads account for the “vast majority” of transportation-related GHG emissions in the U.S.
The GAO studied 10 state DOTs and 10 MPOs. Neither Arkansas nor Montana are currently monitoring road-related GHG emissions. But an MPO in Arkansas told GAO that they plan a $50 million expansion of their bicycle network, and Montana DOT officials said “they will likely consider emissions when developing the state’s carbon reduction strategy.”
Agencies that do track GHG emissions use various data sources. Some base their estimates on the gallons of fuel taxed by the state, while others use traffic counts to model vehicle-miles traveled. Some states and MPOs have established emission reduction targets, the GAO found. For example, the MPO that represents the Washington, D.C. area set seven strategies to reduce on-road GHG emissions 50% by 2030, compared with 2005 levels, including improvement of pedestrian and bike access to transit stations and establishment of a regional electric vehicle charging network.
Last year, the Federal Highway Administration published a proposed rule that would require state DOTs and MPOs to track and reduce GHG emissions, which the FHWA expects to finalize this month. The 2021 infrastructure law provides more than $27 billion in federal funding toward these goals.
Repko said on the podcast that the new report is “part of GAO's broader examination of climate issues,” including climate disaster risk reduction and “efforts to enhance the resilience of transportation infrastructure, such as highways or transit, to better respond to climate change.”