Skip to Content
Streetsblog California home
Streetsblog California home
Log In
Streetsblog USA

Study: Diagonal Intersections Are Especially Dangerous for Cyclists

This week, Cambridge, Massachusetts, unveiled plans for a "peanutabout" that will make a tricky intersection with irregular angles safe for cycling. This type of design intervention could be crucial for locations that new research suggests are especially dangerous.

This new deigned for a diagnoal intersections in Cambridge includes protected bike lanes and a ? on a round-about that locals call a "peanutabout." Image via Boston Cyclists Union
At this irregular intersection in Cambridge, the city plans to improve safety with what the locals call a "peanutabout." Image via Boston Cyclists Union
false

In a study published in the journal Injury Prevention [PDF], a team led by Dr. Morteza Asgarzadeh of Harvard's T. H. Chan School of Public Health found that non-right-angle intersections are especially prone to crashes that cause severe or fatal injuries to bicyclists.

Asgarzadeh and his team mapped 3,300 injury crash locations in New York city involving a motorist and a cyclist. Then they analyzed the relationship between a number of factors and injury severity, including street width, weather conditions, gender and age of the cyclist, and posted speed limit.

In most cases, researchers did not identify a significant link. But the researchers did find that a few conditions are correlated with more severe injuries.

Crashes that occurred at diagonal intersections were 37 percent more likely to result in severe injury or death than crashes at right-angle intersections. In addition, while 60 percent of bike-car crashes happen at intersection, cyclists hit by a cars on straightaways -- not at intersections -- were 31 percent more likely to be killed or severely injured. The researchers hypothesize that crashes on straightways may be more deadly because drivers are traveling at a higher speed.

They also found, not surprisingly, that cyclists struck by a truck or bus driver were twice as likely to be killed as those hit by a car driver.

Asgarzadeh concluded that the findings bolster the case for protected bike lanes, which would shield cyclists on straightaways. They also suggest planning bike routes that have more right-angle intersections and giving cyclists a dedicated signal phase at non-right-angle intersections.

More peanutabouts may also be in order.

Stay in touch

Sign up for our free newsletter

More from Streetsblog California

First OC Streetcar Arrives

The $649 million 4.1-mile OC Streetcar light rail line is 92 percent complete, and now anticipated to open in spring 2026

May 8, 2025

Thursday’s Headlines

California and Trump continue to spar and more news from up and down the state.

May 8, 2025

Talking Headways Podcast: ‘Normal’ is Not Correct, Someone Died Here

After a crash, the debris is quickly cleaned up and everyone moves on (usually too quickly). But these two experts are asking us to all slow down.

May 8, 2025

Metro Names Bill Scott as Chief of Police

Chief Scott and Metro leadership emphasized that keeping Metro transit safe would require a multi-faceted approach that included the deployment of officers as well as collaboration with the community, ambassadors, and service providers. "Sometimes enforcement is the answer," Scott said. "Sometimes it's not."

May 7, 2025

State Supreme Court Reinforces Rules that Cities Must Maintain Safe Roads

When Ty Whitehead was injured in a crash caused by a pothole in Oakland, it sparked an eight-year legal battle that is still being waged.

May 7, 2025
See all posts