Skip to Content
Streetsblog USA home
Streetsblog USA home
Log In
Safety

Compelling Evidence That Wider Lanes Make City Streets More Dangerous

The rate of side impact crashes is lowest on urban streets with lanes about 10.5 feet wide -- much narrower than the standard 12 feet. Graph: Dewan Karim
The safest lane width is narrow, but not too narrow. Graph: Academia.edu

The "forgiving highway" approach to traffic engineering holds that wider is safer when it comes to street design. After decades of adherence to these standards, American cities are now criss-crossed by streets with 12-foot wide lanes. As Walkable City author Jeff Speck argued in CityLab last year, this is actually terrible for public safety and the pedestrian environment.

A new study reinforces the argument that cities need to reconsider lane widths and redesign streets accordingly. In a paper to be presented at the Canadian Institute of Traffic Engineers annual conference, author Dewan Masud Karim presents hard evidence that wider lanes increase risk on city streets.

Karim conducted a wide-ranging review of existing research as well as an examination of crash databases in two cities, taking into consideration 190 randomly selected intersections in Tokyo and 70 in Toronto.

Looking at the crash databases, Karim found that collision rates escalate as lane widths exceed about 10.5 feet.

Roads with the widest lanes -- 12 feet or wider -- were associated with greater crash rates and higher impact speeds. Karim also found that crash rates rise as lanes become narrower than about 10 feet, though this does not take impact speeds and crash severity into account. He concluded that there is a sweet spot for lane widths on city streets, between about 10 and 10.5 feet.

In Toronto, where traffic lanes are typically wider than in Tokyo, the average crash impact speed is also 34 percent higher, Karim found, suggesting that wider lanes not only result in more crashes but in more severe crashes.

The "inevitable statistical outcome" of the "wider-is-safer approach is loss of precious life, particularly by vulnerable citizens," Karim concluded.

Stay in touch

Sign up for our free newsletter

More from Streetsblog USA

Thursday’s Headlines Are Down on the Corner, Out in the Street

Bring a nickel, tap your feet as you avoid having to get into your car to drive out to the big-box strip mall.

October 3, 2024

Room for Improvement: What New York’s Subway System Can Learn from Cities Around the World

New York’s subway was once an international model of modernity. But it's not anymore.

October 3, 2024

Subway Elevators are Not Just a Nice Lift, But a Basic Civil Right

Accessibility is a must-have as cities compete to attract visitors and retain residents.

October 3, 2024

Eight Ways To Reimagine Parking Spaces

This Park(ing) Day, 175 groups across multiple countries transformed curbside parking stalls into bedrooms, terraces, living spaces and more.

October 3, 2024

Week Without Driving Day 2: Where the Sidewalk Ends

A week after I bought my house in Santa Rosa I read in the local newspaper that the city was planning to install a flashing crosswalk on Montgomery Drive.

October 2, 2024
See all posts