The study initially covered 7,670 sections of streets from seven cities in the US; however, it was narrowed down to just 1,117 randomly selected sections with similar characteristics. The researchers focused on the relationship between 20 street design factors and other safety indicators, covering crashes in each section from 2017 to 2019. The data gathered showed that regardless of the lane width, whether 9, 10, or 11 feet, there was no difference in the number of crashes.
However, broader 12-foot lane streets significantly increased the number of accidents compared to narrower-lane roads.
“Our study of city lane widths found that contrary to the current thinking, wider lanes in urban areas can lead to a higher number of crashes and ultimately fatalities,” said Shima Hamidi, PhD, director of the Center for Climate-Smart Transportation at the Bloomberg School. “What if we can narrow lanes without sacrificing safety, and how can we best use the additional space in the existing infrastructure? That’s what we want to know.”