In the quiet city of Keene, New Hampshire—population just under 23,000—a simple traffic innovation is delivering outsized environmental benefits. By replacing traditional intersections with modern roundabouts, Keene is quietly cutting vehicle emissions, reducing air pollution, and proving that small cities can lead the way in climate action.
Roundabouts: More Than Just a Traffic Quirk
For decades, roundabouts were met with skepticism in the U.S., often dismissed as confusing or European. But in Keene, city planners saw their potential early. Today, the city boasts over a dozen roundabouts—more per capita than almost any other American town—and the results speak for themselves.
Unlike signalized intersections where cars idle, accelerate, and brake repeatedly, roundabouts keep traffic flowing at a steady, low speed. This continuous motion dramatically reduces fuel consumption and tailpipe emissions—key contributors to both local air pollution and global greenhouse gas levels.
The Climate Impact of Smoother Traffic
A recent study cited by city officials found that a single roundabout in Keene reduces carbon dioxide emissions by an estimated 15–20 tons annually compared to a traffic-light-controlled intersection . Multiply that across the city’s network, and the climate benefit becomes significant.
Beyond emissions, roundabouts have slashed accident rates by up to 75% for serious crashes, according to the Federal Highway Administration (FHWA) . Fewer collisions mean fewer emergency vehicle trips, less traffic congestion, and even lower emissions from idling during accident clearances.
Why Keene Went All-In on Roundabouts
Keene’s shift began in the early 2000s, driven by a mix of safety concerns and forward-thinking urban planning. “We weren’t just trying to move cars—we were trying to build a safer, cleaner, more livable city,” says former city engineer Mark Roy. “Roundabouts turned out to be a triple win: safer streets, less pollution, and lower maintenance costs.”
Without traffic signals to power or maintain, the city saves thousands in electricity and repair bills each year. The space once occupied by signal poles and turning lanes has been repurposed for trees, native plantings, and pedestrian-friendly landscaping—further improving air quality and urban aesthetics.
A Model for Other Small Cities
Keene’s success hasn’t gone unnoticed. Municipalities from Vermont to Oregon are now studying its approach. The key lesson? Climate solutions don’t always require massive infrastructure or federal grants. Sometimes, they start with rethinking how we move through our own neighborhoods.
“People laugh at first—‘You’re fighting climate change with roundabouts?’” says local environmental advocate Lena Choi. “But when you see the data, and you feel how calm the traffic is, it clicks. It’s elegant, low-tech, and it works.”
What You Need to Know About Roundabouts
- They reduce emissions: Less idling = less CO₂ and NOₓ.
- They’re safer: Lower speeds and fewer conflict points cut crash severity.
- They’re cheaper: No electricity, signals, or complex wiring to maintain.
- They’re greener: Central islands can host pollinator gardens or stormwater capture.
As the U.S. searches for practical, scalable climate solutions, Keene’s roundabouts offer a compelling blueprint—one circular intersection at a time.
