Bike Sharrows Found to Implicate Cyclist Injuries

They might be the cheapest bike infrastructure, but evidence is mounting that bike sharrows do not make cycling in cities any safer.

Bike Sharrows, made official by the Federal Highway Administration (FHA) in 2009, are symbols painted in a lane of traffic meant to be shared by cars and bicycles. They're the cheapest way for cities to increase road safety by directing bicycle traffic, mostly so that cyclists can stay out of the “door zone” and avoid getting clipped by people exiting parked cars. They also indicate to automobile and bus drivers that cyclists have a right to the traffic lane, and to watch out for them, which perhaps cues drivers to give cyclists they pass wider berth.

In a previous Gov1 story, Data Solutions for Reducing Bicycle Crashes, 2015 bicycle injury research showed that in the vast majority of bicycle crashes, the motorists involved did not see the cyclists before impact. That's regardless of whether traffic lanes are unmarked or contain bike sharrows, painted bike lanes or cycle tracks.

Even with a super sharrow--white bike sharrows painted on a wide, colored line in the center of a traffic lane--safety results are mixed. A 2013 study by Oakland, Calif., found that the super sharrow:

  • Led cyclists to ride farther from the door zone than they did with standard bike sharrows
  • Had no negative effect on auto operations or transit speed
  • Did not significantly change the average passing distance for motorists who overtook cyclists
  • Decreased the percentage of motorists that leave three feet or more when passing cyclists

That study also found that all sharrows led motorists to switch to the left travel lane than they did with no bicycle markings.

More recently, University of Colorado Denver analyzed bike infrastructure from 2000 to 2010 at thousands of blocks in Chicago. The researchers analyzed several factors, such as where bike sharrows and bike lanes were installed and where there was no bike infrastructure, bike commuting rates and street collision data. What they found is that bike lanes encouraged more bike riders and that the rate of injuries declined the least with sharrows:

  • Cyclist injuries on roads with bike lanes decreased 42 percent
  • Cyclist injuries on roads with sharrows decreased 20 percent
  • Cyclist injuries on roads lacking bike infrastructure decreased 37 percent

In addition to possibly decreasing the likelihood that drivers will give cyclists wider berth when passing them, bike sharrows might be "more dangerous than doing nothing," according to these university researchers. They presented their findings to the Transportation Review Board, according to CityLab, calling on the Federal government to expose sharrows as the "cheap alternative that not only fails to solve a pressing safety issue, but actually makes the issue worse through a sense of false security."

StreetsblogUSA considers sharrows the "dregs" of bike infrastructure, and its coverage of the research not only questioned the ethics of continued use of sharrows, but said it calls for more appropriate bike infrastructure. The blog has been covering transit trends that relate in part to improving conditions for pedestrians, cyclists and transit riders.

According to the National Association of City Transportation Officials, more than 26 states were already using sharrows by the time it was approved by FHA.

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