Issue Brief: Estimating the Greenhouse Gas Impact of Federal Infrastructure Investments in the IIJA

December 21, 2021

NOTE: This is a summary page -- follow this link to read the full analysis.

By any measure, the Infrastructure Investment and Jobs Act (IIJA), the bipartisan infrastructure package signed into law by President Biden on November 15, represents a historic investment in the underpinnings of our economy, especially when it comes to transportation. The bill authorizes roughly $1 trillion over five years, nearly $600 billion of which is surface-transportation related. That infusion of money over the next five years has the potential to catalyze transformative changes in the ways people and goods move, and to help make our transportation system safer, more reliable, more affordable and more equitable. It will also have a lasting effect on U.S. greenhouse gas emissions. The White House and congressional leaders have cited addressing climate change and equity among the goals of the IIJA.

To understand how the IIJA’s historic investments in transportation infrastructure could help — or hinder — efforts to achieve the GHG reduction goals that states and the federal government have set, the Georgetown Climate Center analyzed the bill using our Transportation Investment Strategy Tool and assessed the potential effects of each of the bill’s surface transportation provisions.  

We found IIJA could be an important part of the U.S. response to climate change. Or it could lead to more greenhouse gas pollution than the trajectory we are currently on. Where the actual outcome falls within that range will depend on the decisions made by state, federal, and local governments about how to spend the money made available by IIJA. 

  • If transportation investment decisions prioritize a “fix it first” approach and emphasize maintenance of existing roadways, along with investments in transit, electric vehicles and charging infrastructure, and other low-carbon transportation options, this historic infusion of federal funding has the potential to accelerate reductions in GHG emissions from surface transportation relative to business as usual.
  • But if investments instead flow mostly to adding more lanes and building more roads, the IIJA funding could result in an increase in emissions over what we’d expect without this additional investment. That’s because building more roads consistently results in more traffic — an “if you build it, they will come” effect known as “induced demand.” In short, traffic expands to fill the new lanes within a few short years, bringing with it more pollution.


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