Above photo: Seattle’s first downtown protected bike lane, which opened in 2014. Seattle DOT.
New research shows that by slowing cars at intersections, bike lanes increase safety for all road users.
In 2022, 1,360 people in the U.S. died preventable deaths while riding a bike. One of the most deadly, and most common, types of bike crashes is known as a right hook: A driver turns right directly into the path of a cyclist going straight through an intersection, hitting them or causing them to crash.
Researchers at Rutgers University wanted to test if installing bike lanes at an intersection could reduce vehicle speeds, particularly for drivers turning right. Using chalk paint spray, traffic cones and plastic bollards, they installed temporary bike lanes near an intersection in Asbury Park, New Jersey.
Then, they used computer vision technology to track the speed and path of more than 9,000 vehicles. Researchers compared speeds under three conditions: no bike lanes, painted bike lanes and painted bike lanes with delineators (traffic cones and bollards).
The results, published recently in the Journal of Urban Mobility, were striking: Both painted and delineated bike lanes slowed drivers, especially when they were turning right.
For the experiment, researchers temporarily removed nine parking spaces to create 6-foot wide bike lanes with a 3-foot buffer between bike and car travel lanes. Car travel lanes were reduced by at least one foot each, a decrease that has been shown to reduce crashes. In addition, the bike lanes created a sharper turning radius for drivers turning right, another intervention that might force drivers to slow down.
One finding: Bike lanes with physical delineators (cones or bollards) were more effective than paint-only lanes at calming traffic, echoing a popular mantra for bike activists: “Paint is not protection.” (The lanes were not protected, however, because drivers could drive over the delineators.) For vehicles turning right, top speeds were reduced by 28% and average speeds by 21%. Paint-only bike lanes slowed driver speeds by up to 14% and drivers going straight slowed down by up to 8%.
“In order to achieve Vision Zero initiatives, planners and policy makers should focus efforts on delineated bike lanes, not merely painted lanes,” researchers concluded. “The costs associated with the materials are offset by the traffic calming benefits of the delineated bike lane.
The study adds that pop-up bike lanes are a cost-effective solution for studying the effects of more permanent solutions — after all, you could just borrow the traffic cones. A city could quickly implement pop-up or temporary infrastructure. Then, armed with data and community feedback, they could invest in making the changes permanent.
Pop-up traffic interventions were popular during the early days of the Covid-19 pandemic as cities sought to provide socially distant spaces for people to go outside and recreate, notes the study. According to researchers, the new cycling infrastructure was successful in encouraging more people to ride bikes, a form of transportation that is also more climate-friendly.
This story was produced through our Equitable Cities Fellowship for Social Impact Design, which is made possible with funding from the National Endowment for the Arts.