BikePortland

What’s behind city’s confidence in ‘crossbikes’? This research


Taken from Frank Boateng Appiah’s paper.

What Portland’s crossbike markings lack in legal authority, they make up for in research.

After recently hearing a positive comment from PBOT Bike Coordinator Roger Geller about the effectiveness of these painted crosswalks for bike users, I heard about a study that backs it up. Now that I’ve tracked down that study, Geller’s confidence is much more understandable.

The study comes in the form of new research titled, Improving Safe Bicycle-Crossings at Unsignalized Intersections through Pavement Markings: Analysis of the City of Portland Innovative Strategy by Frank Boateng Appiah. Appiah completed the research as part of his work toward a Master of Science in Civil and Environmental Engineering at Portland State University. Among the thesis committee members who reviewed the work was noted bicycle researcher Christopher M. Monsere, who’s worked with PBOT on many bikeway innovations in the past including bike boxes and blue signal detection lights.

For this study on crossbikes, Appiah analyzed before and after video data of three intersections: NE Going at 15th, SE Salmon at 20th, and NE Holman at 33rd. At each location, his research showed significant improvement in the rate of car users who yielded to people on bikes. In addition to increased yielding rates, he also tracked the amount of times a bicycle user had to wait for cars to clear the intersection. (Waiting is a key metric, because research shows when people are forced to wait too long, they are more likely to break the law or make a bad decision.)

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Here’s what he found on yielding behaviors:

At NE Going and 15th, before the crossbike was striped drivers would yield at a rate of 48% and 61% (from the near and far side of the intersection, respectively). After the crossbike markings went in, those rates shot up to 91% and 95%. At NE Holman and 33rd driver yielding went up from 38% and 36% to 77% and 82% after the treatment was installed. At SE Salmon and SE 20th drivers only yielded 21% and 11% of the time before the crossbike went in, rates that doubled for the near side and tripled for the far side afterwards.

When it came to how many bicycle users had to wait for drivers to clear the intersection, the crossbike markings also had a big impact: At Going and 15th, bicyclists on the near-side of the intersection would wait for cars 52% of the time. That was slashed to just 9%. At SE Salmon and 20th, the rate of bicycle users who had to wait for cars was reduced from 79% to 60% on the near side and 89% to 67% on the far side.

Another bonus of the bike markings Appiah noticed was that they helped orient riders into a safer spot to wait that gave them a more efficient path to cross.

While some Portlanders remain skeptical of these markings because they have no legal authority (unlike the crosswalks they’re painted next to), this research will likely make crossbikes even more popular with PBOT, who clearly sees them as a relatively quick and cheap way to improve the bike network.

Delve deeper into the research by downloading it here.

— Jonathan Maus: (503) 706-8804, @jonathan_maus on Twitter and jonathan@bikeportland.org
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