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Home / Johns Hopkins University

Traffic lanes: the narrower the better?

By Suzanne Potter, Producer

Redrawing some California traffic lanes to make them narrower would make many city streets safer according to a new study from Johns Hopkins University. Many U.S. street lanes are 11 to 12 feet wide, but researchers found that 9 foot lanes on streets where the speed limit is 30 to 35 have significantly fewer crashes.

Professor Shima Hamidi, Bloomberg assistant professor and director, Center for Climate Smart Transportation, Johns Hopkins University and coauthor of the study, said when the lanes are narrower, drivers tend to be more cautious – allowing them to catch any unexpected error and prevent a crash.

“When streets become wider, then it gives the drivers this false sense of safety that makes them drive faster. And that speed is really the main cause of crashes, ” Hamidi explained.

Traffic deaths in California shot up more than 7% and pedestrian fatalities increased more than 9% from 2020 to 2021. The study found that narrowing the lanes makes it possible to cheaply add bike lanes and sidewalks, which encourage people to drive less, which reduces congestion and carbon emissions.

Hamidi said until now, American urban planners have shied away from making lanes narrower for fear of increasing crashes, but she hopes this new data, plus traffic studies from other parts of the world, will be reassuring.

“When you compare streets in American cities versus their European counterparts, you see that they are significantly wider. And we don’t have that safety issue in European cities,” Hamidi continued.

The study also found that narrowing street lanes does not increase congestion.

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