STUDY: Narrow City Streets Are Safer Than Wide Ones

STUDY: Narrow City Streets Are Safer Than Wide Ones

The Johns Hopkins study may have civil engineers rethinking the foundation of street design and lane-width guidelines.

A Johns Hopkins Bloomberg School of Public Health study may make us rethink how we look at roads. The study has broken the notion that wider roads are safer since there’s more room for mistakes, making accidents less likely.

While cars are getting safer, the researchers found that shrinking lane widths with context-appropriate speed limits proved safer than roads with wider lanes.

Traffic fatalities are the leading cause of death for people aged 1-54 in the US. The country also has the highest traffic fatality rates among developed countries: 11.6 deaths per 100,000 people versus other European countries, which are only 1.3 to 3.2. Pedestrian and cyclist deaths are also rising, as reflected in a recent study by the Insurance Institute for Highway Safety, which found vehicles with blocky fronts, such as America’s best-selling Ford F-150, dangerous to other road users.

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.”

The researchers also focused on speed limits along these streets. They found that making lanes wider at lower speeds of 20-25 mph made no difference in safety. However, the danger factor increases if these speed limits are raised to 30-35 mph on roads with a lane width between 9-12 feet.

The researchers determined that wider roads with higher speed limits are 1.5 times more likely to have an accident, proving that these roads only let drivers drive faster and aren’t safer despite the government pushing for cars to be safer for pedestrians.

While there is still a worry about traffic congestion, Hamidi has stated that these narrower lanes will slow the traffic speed and not add to it. Reducing these lanes will have the benefit of helping people transition to other modes of transportation, such as biking and walking, which can help reduce greenhouse gas emissions.

“The best form of traffic calming in a street that cannot accommodate speed control devices (and even those that can), may be lane narrowing,” said Jonathan Larsen, Transportation Division Director, Salt Lake City Corporation.