Study Analyzes Dangers of Painted Bike Lanes


A new analysis from researchers at Emory University in Atlanta found that painted bike lanes demonstrated "estimated harmful effects,” meaning drivers may be crashing into riders more than they would if there wasn't any paint on the ground.

According to a report from StreetsBlog USA, the study published in the Journal of Transport and Health found that even protected bike lanes that give way to paint at intersections could be a danger to riders. 

About the Analysis

To perform the analysis, researchers reportedly searched through almost two years of police reports and bicycle ridership data in the city of Atlanta.

The analysis intended to estimate per-mile crash rates along streets with a number of different types of bike infrastructure, including sharrow marking, painted lanes that run alongside traffic, painted lanes with buffer zones, as well as protected on-street bike paths and off-street trails.

Researchers then created an advanced model based on surrounding corridor data and other factors to estimate what each of those bike routes' crash rates would have been if they had no bike infrastructure at all. Afterwards, the researchers reportedly compared those rates with real-world data to get an idea of what kind of interventions are saving the most lives.

The authors of the study, however, noted that their analysis carries some unknowns.Because good bike data is reportedly so difficult to find in the U.S., the researchers only had access to limited data in a small region of just one city without many on-the-ground bike counters.

Additionally, researchers had reportedly gathered any info they could source off the biking app Strava, which tends to attract recreational riders more than everyday transportation cyclists.

The report added that, even after controlling for area-level household income and area-level population density,  paint-only lanes and sharrows still seemed to be more dangerous than roads with nothing at all.

The researchers say that they weren't totally sure why this was the case, especially considering that earlier studies in other communities have come to the opposite conclusion.     

"It could be that the prototypical strong and confident cyclist is more likely to use the painted bike lane, and that drivers expect the cyclist to know what to do and get out of the way," said Michael Garber, a postdoctoral fellow at UC San Diego and the lead author of the study.

"But I'm really not sure. At least anecdotally from riding in Atlanta, it does seem to me that it's more often unhoused people and other people who seem to be more disadvantaged who end up using bike lanes in high car traffic."

Garber claimed Atlanta's paint-only lanes are potentially so dangerous due to the tendency of being striped on roads that are already dangerous. The National Association of City Transportation Officials' standard design guide advises transportation officials to paint "conventional" bike lanes only on relatively narrow roads with "few cars and prevailing vehicle speeds under 25 miles."

However, the researchers noted that "several buffered and conventional bike lanes in the study area fail[ed] on all counts," including one particularly bad arterial that reported five times more average annual daily traffic than the guide recommended for any road with a paint-only bike lane.

"As someone who rides a lot, I avoided conventional bike lanes in Atlanta for that reason," said Garber. "It just put me too close to a really dangerous conflict zone."

However, the report adds that even on Atlanta's best-protected bike paths riders aren't necessarily safe—at least if they must cross an intersection where their protection abruptly stops.

Garber explained that the delineated lanes in the Atlanta sample gave way to standard crosswalks at multiple points, and that crossings didn't have safety features like corner islands to tighten a motorist's turning radius and make them more likely to see an oncoming rider. Without these features, it was typical to see drivers blocking the entrances and exits to bike lanes, potentially forcing riders to make dangerous maneuvers around them.

Additionally, protected bike lanes were still reportedly rare in Atlanta at the time as there were around three miles of them in the whole city when the analysis was conducted.

The report adds that the fact that local transportation officials favored potentially confusing two-way cycle tracks over one-way lanes that follow the same direction of travel as cars, and Garber suspects some drivers were legitimately surprised to see riders in their path until they got used to seeing more of them around.

"I think there’s evidence that conventional bike lanes don’t do much to improve safety, and may actually harm safety in certain situations," he added. "Basically, this study bears out the idea that paint is not protection."


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