The Connection Between the Urban Heat Island Effect and Highway Construction
Helicopter Aerial View of the famous Los Angeles Four Level freeway interchange. Getty Images
Recent research from CSSH/CEE Associate Professor Serena Alexander explains the impact of highway construction on urban “heat islands” and proposes initiatives to mitigate the consequential uptick in temperature from these projects.
This article originally published on Northeastern Global News. It was published by Cody Mello-Klein.
Is highway expansion heating up our cities?
When singer-songwriter Joni Mitchell railed against environmental destruction in her 1970 song “Big Yellow Taxi,” she cautioned against paving paradise and putting up a parking lot. But she might have been better off warning about highways.
U.S. cities are rapidly becoming urban heat islands, where these cities are significantly warmer than their surrounding area. Vast expanses of asphalt and concrete trap heat, while large, densely packed buildings disrupt wind flow and intensify the effect. But beyond parking lots and skyscrapers, recent research points to highways as another cause behind America’s urban heat islands.
By studying satellite-based temperature data before and after 11 major highway expansion projects in the San Francisco Bay Area, researchers found all the projects had “significant and measurable” impacts on the urban heat island effect, said Serena Alexander, an associate professor of public policy, urban affairs and civil and environmental engineering at Northeastern University.
These highway projects, which involved everything from adding lanes to installing guardrails, accounted for 70-88% of the intensifying heat disparity researchers found through their analysis.
“I’m not trying to argue we shouldn’t build highways,” Alexander said. “We have to be aware of these impacts and where we can mitigate [them].”
In the U.S., building highways has traditionally been viewed as a way to alleviate traffic and connect communities. The latter justification is true, but the former has more recently come under fire as civil engineers have come to see traffic return to pre-construction levels as more drivers take to the road, Alexander explained.
Highway construction nonetheless remains a leading form of infrastructure investment in the U.S. As of January 2026, there were nearly 115,000 new highway projects underway in the U.S., accounting for $257 billion in federal funds, according to the American Road and Transportation Builders Association.
This research focused on California for a specific reason: The state has experienced major highway expansion as the population has boomed over the last decade. Between 2018 and 2023 alone, the California Department of Transportation added 550 lane miles, enough to stretch from Mexico to Oregon, according to state data.
Read full story on Northeastern Global News