From the U.S. Government Accountability Office, www.gao.gov Title: Are Efforts to Reduce Emissions through Road Projects Working, Cost Effective? Description: Cars, trucks and other vehicles are a major source of emissions that have had serious consequences on air quality and people's health. One study estimates that these emissions will contribute to as many as 18,000 premature deaths in the U.S. this year. Since the 1990s, the Department of Transportation has been working with states to cut emissions by supporting projects that would reduce traffic congestion. We'll learn more about these efforts from GAO's Biza Repko. Related work: GAO-25-107366, Federal Highways: DOT Should Improve Communications on Its Cost-Effectiveness Tool for Emissions Reductions Released: June 2025 [ START ] {Music} [Elizabeth "Biza" Repko:] Department of Transportation could more consistently communicate with the states to help them better consider cost effectiveness when they're selecting projects. [Holly Hobbs:] Welcome to GAO's Watchdog Report. Your source for fact-based, nonpartisan news and information from the U.S. Government Accountability Office. I'm your host, Holly Hobbs. Cars, trucks and other vehicles are a major source of emissions that have had serious consequences on air quality and people's health. One study estimates that these emissions will contribute to as many as 18,000 premature deaths this year in the U.S. alone. Since the 1990s, the Department of Transportation has been working with states to cut emissions by supporting projects that would reduce traffic congestion. We'll learn more about these efforts from GAO's Biza Repko, who has a new report out on this issue. Thanks for joining us. [Biza Repko:] Thanks for having me. [Holly Hobbs:] Biza, maybe we can start with what is this partnership between the U.S. Department of Transportation and the states? [Biza Repko:] Sure. So, the program is called the Congestion Mitigation and Air Quality Improvement Program. It's also known as CMAQ. And it started back in 1991. And the purpose of it is a way for the federal government, through state departments of Transportation, to provide money to states to help meet Clean Air Act requirements. And what they're trying to do there is reduce congestion and improve air quality by reducing transportation emissions. It provides about $2.5 billion to states every year, and they can either spend it themselves or they can pass it along to regional entities in the state to spend the money. [Holly Hobbs:] Do we know how this funding has been used so far? [Biza Repko:] We do. So, we took a look at the projects that the Department of Transportation has funded since 2015. And about 80% of them fall into three buckets. The first bucket is traffic flow improvement. So that's things like you're building like a roundabout at an intersection, or you're doing something like synchronizing traffic lights. And the point of all of that is to improve traffic flow. Second bucket--Bicycle and Pedestrian projects. Those are things like you're going to improve the sidewalk or you're going to build bike lanes, or even bike sharing could be a service. Third bucket--transit projects. You're going to do something like new bus or rail service, or even improve existing stations to make them more attractive to riders. And the point of those projects is to take people out of their cars and put them in a different mode of transportation that has fewer or no emissions. [Holly Hobbs:] So these projects, they help reduce traffic. They can improve air quality. It all sounds like good news. Why was GAO asked to look into this? [Biza Repko:] Well, like I said before, this program has been around for over 30 years and Congress just wanted us to take a look at it. They wanted to understand how the funding is being used and how cost effective the projects are at reducing emissions. [Holly Hobbs:] So what did we find? [Biza Repko:] So two major things. First, those buckets of projects that I talked about--they have helped over time reduce emissions of a number of different types of pollutants that are caused by transportation. But second, related to cost effectiveness, we found that the projects could be doing better. Most of the projects that we looked at have not been very cost effective at reducing emissions. So I'll take a step back. To do that, we took a look at reports that the Department of Transportation issues. And in those reports, it rates the cost effectiveness of different types of projects. We found that 90% of the projects that were funded since 2015 were of a project type rated by DOT as either mixed or weak cost effectiveness. [Holly Hobbs:] So is the Department of Transportation working with states on this issue of cost effectiveness? [Biza Repko:] They are. Like I said, they issue those reports every few years, which is trying to provide information to states on projects that would be the most cost effective. They also provide a series of tools to states--like calculators they can use--and these help them estimate emissions reductions from their projects. And as part of our work, we surveyed all the state DOTs and asked them about these tools. And we found that the states have used them and they do find them helpful. {Music} [Holly Hobbs:] So Biza just told us that efforts to reduce harmful emissions through projects that would address traffic congestion are working, but they may not be as cost effective as they could be. So Biza, what more do we think the Department of Transportation should be doing to help states improve their efforts and their use of funds? [Biza Repko:] Well, we think the Department of Transportation should improve its communication to the states. You remember that cost effectiveness report I talked about? The last time they issued one was in 2020. And since then, you know, they haven't really consistently communicated to states about that resource. When we did our survey, we found that one third of the state departments of transportation were unaware of it. So we'd like to see them better informed. And part of the reason is we found that states that were aware and used that resource picked more cost effective projects. So we made a recommendation to the Department of Transportation to communicate more consistently on the effects of that report with the states. [Holly Hobbs:] And last question, what's the bottom line of this report? [Biza Repko:] The bottom line is that the program has funded a wide range of projects, and a lot of them have been helpful in reducing emissions and improving congestion. But Department of Transportation could more consistently communicate with the states to help them better consider cost effectiveness when they're selecting projects. [Holly Hobbs:] That was Biza Repko talking about our new report on emission reduction projects. Thanks for your time, Biza. [Biza Repko:] Thanks for having me. [Holly Hobbs:] And thank you for listening to the Watchdog Report. To hear more podcasts, subscribe to us on Apple Podcasts, Spotify or wherever you listen. And make sure to leave a rating and review to let others know about the work we're doing. For more from the congressional watchdog, the U.S. Government Accountability Office, visit us at GAO.gov. [ END ] For more info, check out our report GAO-25-107366 at: GAO.gov