Science Friday

Why Do We Keep Widening Highways If It Doesn’t Reduce Traffic?

Nov 11, 2024

Megan Kimble, journalist and author of City Limits: Infrastructure, Inequality, and the Future of America’s Highways, dives into the perplexing issue of highway expansion and its failures to ease traffic. She discusses how more lanes often lead to increased congestion and pollution, particularly affecting marginalized communities. The conversation highlights the movement to remove highways in favor of greener, community-focused designs. Kimble advocates for prioritizing public transit as a solution for better urban living and reveals shifting perspectives to create more walkable neighborhoods.

17:48

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Megan Kimble

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Episode notes

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Quick takeaways

Highway expansion fails to alleviate traffic congestion; instead, it leads to increased travel times due to induced demand behavior changes.

The environmental impact of highway widening is significant, contributing to greenhouse gas emissions and undermining climate action efforts by states.

Deep dives

The Ineffectiveness of Highway Expansion

Expanding highways is often perceived as a straightforward solution to traffic congestion, but research shows that this approach tends to exacerbate the problem. Historical data indicate that as road capacity increases, so too does traffic volume, a phenomenon known as induced demand. The more lanes that are added, the more commuters shift their behaviors, leading to longer travel times and increased congestion. Ultimately, the intended effect of alleviating traffic just does not materialize, leading to a paradox where more lanes create more traffic woes.

Intro

2min

The Paradox of Highway Expansion

11min

Transforming Cities: The Rise of Highway Removal

2min

Reviving Urban Spaces: The Anti-Highway Movement

4min

Shifting Perspectives on Highways and Urban Living

3min

Have you ever been stuck in traffic and thought, if only this highway was a little wider so it could fit more cars? You aren’t alone.

Many states have been expanding their highways. New York Governor Kathy Hochul recently announced a $1.3 billion project to expand one of the state’s highways for an estimated maximum six-minute travel savings. Other highway-widening projects are underway in Texas, California, and Maryland. In 2022, federal, state, and local governments in the US spent $127 billion on highway construction. Some departments of transportation say expanding highways is necessary to reduce congestion, especially in areas with growing populations, and to encourage economic development.

But decades of research shows the opposite effects when highways are expanded—that travel times actually increase when more lanes are added. So how does this happen, and why do we keep expanding highways even though the research says it doesn’t work?

Megan Kimble, journalist and author of City Limits: Infrastructure, Inequality, And The Future Of America’s Highways, joins Ira to break down the research behind highway widening and discuss how increasing funding for public transit could help make traffic better, and why some cities are deciding to remove their highways entirely.

Read an excerpt from City Limits: Infrastructure, Inequality, And The Future Of America’s Highways.

Transcript for this segment will be available after the show airs on sciencefriday.com.

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