Wider Traffic Lanes Are More Dangerous

Researchers out of Johns Hopkins University are hoping to make nine the new magic number in urban design. After analyzing 1,117 streets in seven cities, from DC to Dallas, they found that wider traffic lanes have significantly more pedestrian accidents than lanes shrunk down to 9 feet. Per Johns Hopkins' Bloomberg School of Public Health, transportation departments have preferred lane widths between 11 feet and 12 feet, assuming the extra space enhances safety for pedestrians and cyclists. But wider, 12-foot lanes, which "accommodate fast and convenient driving," saw 1.5 more accidents when speed limits were 30mph or 35mph, a report on the findings says (collision rates were similar in lower speed limits).

The study's lead author, Shima Hamidi, stresses the importance of prioritizing inclusive street design over driving speed and functionality. She told NPR she was "shocked" to learn that traffic collisions were the leading cause of death for people up to age 54 in the US. "And the main reason is the lack of pedestrian and cyclist infrastructure," she noted. Pedestrian fatalities saw a sharp increase—more than 40%—from 2010 to 2018, and 2020 was the deadliest period for pedestrians in 40 years. Streets marked 35mph and under have more cyclists and pedestrians active because the lower speed limits feel safer, the study noted, but widening lanes give some drivers the green light to speed.

"The report's findings really track what we and other safe streets advocates have been saying for a while, which is when you design streets so that cars can go more quickly, then you have far more crashes," says Jessica Hart of Families for Safe Streets. Reducing city traffic lane width could not only decrease collisions, but it would also make room for additional safety features like bicycle lanes and wider sidewalks. And with the dismal stats around pedestrian safety, the researchers believe that thinner lanes are one of the cheapest ways to get results quickly. "Lane-width reduction is the easiest and most cost-effective way to accommodate better sidewalk and bike lanes within the existing roadway infrastructure," says Hamidi. "Narrower lanes ultimately minimize construction and road maintenance and also reduce environmental impacts." (More stories on road safety).