Research Shows More Roads = More Driving

A national study shows, once again, that increasing road supply induces additional vehicle travel, particularly over the long run.

1 minute read

March 23, 2025, 11:00 AM PDT

By Todd Litman


Close-up of rear car bumper in traffic on freeway.

Kara / Adobe Stock

A new study, Road Capacity as a Fundamental Determinant of Vehicle Travel, published by  the University of California Institute of Transportation Studies, indicates that roadway supply is a key factor affecting the amount that people drive in a community. It uses U.S. national data to analyze factors that affect vehicle travel. It finds that road capacity has a larger effect on per capita VMT than factors traditionally considered, such as income and fuel prices. This provides aggregate evidence that roadway expansions induce additional vehicle travel, particularly over the long run.

Road supply does not just affect traffic speeds and automobile accessibility but also impacts pedestrian connectivity, land development, transit service feasibility, plus household residential and employment location decisions. The researchers point out that per capita vehicle travel peaked early in the Twenty First Century so road capacity rather than income or fuel price has emerged as the fundamental factor affecting vehicle travel. 

The study concludes that achieving VMT reduction targets are likely to require road capacity reductions.

Friday, February 28, 2025 in Road Capacity as a Fundamental Determinant of Vehicle Travel

portrait of professional woman

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching. Mary G., Urban Planner

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching.

Mary G., Urban Planner

Get top-rated, practical training

Close-up of "Apartment for rent" sign in red text on black background in front of blurred building

Trump Administration Could Effectively End Housing Voucher Program

Federal officials are eyeing major cuts to the Section 8 program that helps millions of low-income households pay rent.

April 21, 2025 - Housing Wire

Logo for Planetizen Federal Action Tracker with black and white image of U.S. Capitol with water ripple overlay.

Planetizen Federal Action Tracker

A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.

April 30, 2025 - Diana Ionescu

Ken Jennings stands in front of Snohomish County Community Transit bus.

Ken Jennings Launches Transit Web Series

The Jeopardy champ wants you to ride public transit.

April 20, 2025 - Streetsblog USA

Close-up of white panel at top of school bus with "100% electric" black text.

Driving Equity and Clean Air: California Invests in Greener School Transportation

California has awarded $500 million to fund 1,000 zero-emission school buses and chargers for educational agencies as part of its effort to reduce pollution, improve student health, and accelerate the transition to clean transportation.

7 hours ago - California Air Resources Board

Aerial view of Freeway Park cap park over I-5 interstate freeway in Seattle, Washington at night.

Congress Moves to End Reconnecting Communities and Related Grants

The House Transportation and Infrastructure Committee moved to rescind funding for the Neighborhood Equity and Access program, which funds highway removals, freeway caps, transit projects, pedestrian infrastructure, and more.

April 30 - Streetsblog USA

"No Thru Traffic - Open Streets Restaurants" sign in New York City during Covid-19 pandemic.

From Throughway to Public Space: Taking Back the American Street

How the Covid-19 pandemic taught us new ways to reclaim city streets from cars.

April 30 - Next City