CU Denver study: Cities with protected bike lanes are safer for cyclists and drivers

Denver is working on installing additional lanes this year.
5 min. read
Double protected bike lanes on South Broadway. (Kevin J. Beaty/Denverite)

Research shows that biking around a city is more dangerous than driving, so University of Colorado Denver associate professor Wesley E. Marshall decided to test out an idea: more cycling makes more dangerous cities.

But it turned out "the opposite is true," Marshall said.

The civil engineering professor had previously published a paper looking at transit options in cities and wanted to take a closer look to learn more about the relationship between safety and transit options. His findings suggest cities with bike protection infrastructure tend to make things safer not just for cyclists but for people using all other modes of travel -- and that Denver is "headed in the right direction."

"I guess our hypotheses was maybe safety in numbers," Marshall said. "Like, you've got a lot more cyclists on the road, drivers behave differently. There might be some sort of traffic calming in themselves, in terms of slowing."

What they found was that it wasn't so much that more cyclists meant safer roads, it was that the infrastructure built for them. That includes protected bike lines including cycle tracks, which Marshall said were the biggest factors in overall road safety. The bike lane infrastructure act as "calming" mechanisms on traffic, slowing cars and reducing fatalities.

"The reality is that the whole city ends up being safer when you have a city with a lot of bicycling, and the infrastructure you build to bring cyclists seems to be the biggest factor," Marshall said.

Cyclists speed by Denver Parks and Recreation's safety booth on the Cherry Creek Trail, May 16, 2019. (Kevin J. Beaty/Denverite)

The study didn't set out to "rank" cities from bad to worse. The researchers looked at 12 major cities, including six who had significant increases in bike mode share and six who had not had a significant increase over the period between 2000 and 2012. Denver was among those who saw an increase over that period.

The study focused on that 13-year time period based on the availability of non-fatal crash data, but also included a wider look: from 1990 to 2010. In that time, Denver saw fatal crashes drop 40.3 percent. Portland, Oregon saw the biggest change. Bike mode share increased from 1.2 percent to 6 percent while the road fatality rate dropped by 75 percent.

Marshall cited New York City and Davis, California, as cities where they're doing a good job of improving protective bike lanes.

Marshall said they used both federal and state data to complete their research while speaking to local planners and getting crash data from individual cities.

His research is set to be published Wednesday in the Journal of Transport & Health. The study was conducted jointly by Marshall and University of New Mexico assistant professor Nicholas N. Ferenchak. They believe the study is one of the most comprehensive looks at bicycle and roads safety in the country.

Denver has 10 protected bike lanes, according to the city's website.

The city defines protected bike lanes as a "dedicated path for people on bikes to travel along on a street that provides a buffer of protection between them and passing traffic."

There are plans for additional bikes lanes. Marshall thinks its a step in the right direction, coupled with the city's Vision Zero initiative, but he believes this process is too slow.

"We've added a handful of sort of protected bike lanes," Marshall said. He added, "I think Denver needs to do a better job of building real, protective bike infrastructure.

The city will be installing 16.9 new bikeways miles along nine city streets this year, according to the Public Works Department.  Funding for the new bike lanes comes through the Elevate Denver Bond Program and the department's own annual bike program. The bond program will provide $18 million to partially fund Denver Public Works' plans to install 125 miles of new bikeways over the next five years

David Pulsipher focuses on pedestrian and bicycling planning as a supervisor with the city's public works department. Their biggest goal is getting everyone in Denver within a quarter mile of a "high comfort bike facility," which is defined as a protected bike lane with some kind of vertical element separating cyclists from vehicle traffic and neighborhood bikeways with streets designed to encourage bike travel.

Pulsipher said U.S. Census data suggests less than 3 percent of Denver residents commute to work on a bike. But he feels this number is probably underreported.

"We find that people generally like to ride in their local streets," Pulsipher said. "We really want to encourage people to ride bikes that may not be riding bikes right now. We feel like giving people high comfort facilities will encourage them to do that now."

Overall, Denver currently has 184 lane miles of on-street bikeways in the city. That includes 39 miles of sharrows, which Marshall said are shared lanes with chevron markings on roads that don't include a physical barrier. They were invented in Denver, but Marshall said he doesn't think they're very effective. A study he completed examing at Chicago's lanes showed they were doing more harm than good.

Last month, bike activists calling for safer lanes placed red Solo cups stuffed with tomatoes along bike lanes to show how easily the lines are breached by cars. It was part of a worldwide day of action commemorating a bike advocate in Washington who was killed by a driver last month while riding inside a painted bike lane.

Recent Stories