Friday, October 25, 2013

UC Study: Riding a bike in SF more dangerous than we thought


The NY Times story the previous post is based on includes this:

Dr. Rochelle Dicker, a trauma surgeon at the University of California...cares for victims of the worst bicycle injuries, people who might need surgery and often end up in intensive care. So she decided to investigate those crashes. She and her colleagues reviewed hospital and police records for 2,504 bicyclists who had been treated at San Francisco General Hospital. 

She expected that most of these serious injuries would involve cars; to her surprise, nearly half did not. She suspects that many cyclists with severe injuries were swerving to avoid a pedestrian or got their bike wheels caught in light-rail tracks, for example. Cyclists wounded in crashes that did not involve a car were more than four times as likely to be hurt so badly that they were admitted to the hospital. Yet these injuries often did not result in police reports---a frequent source of injury data---and appeared only in the hospital trauma registry. Dr. Dicker is not a cyclist, but she said, “Lots of my colleagues do not want to ride after seeing these injuries.” (emphasis added)

Dr. Dicker's study confirms what cycling experts say about "solo falls," though it found a lot more vehicle/bike collisions than expected.

The SFBC's favorite bike safety instructor, Bert Hill, tells us that 45% of all cycling accidents are "solo falls" and that only 18% involve another vehicle ("Mission: Not Impossible," Paul McHugh, Feb. 17, 2005, SF Chronicle). And John Forester: "When you mention cycling accidents, most people assume that you mean car-bike collisions, because this is the only kind they worry about. This is wrong, because car-bike collisions account for only about 12% of cycling accidents" (Effective Cycling, page 262). Robert Hurst, a long-time bike messenger and author, in his book on urban cycling, The Art of Cycling, tells us that collisions with vehicles "account for no more than about 15 percent of all cycling accidents" (page 161).

At my request, Dr. Dicker sent me a copy of her study, which found that cycling accidents are consistently under-reported in San Francisco (the study didn't include accidents outside the city):

Underestimation of crash rates results partly from a lack of recorded data on cyclist-only (CO) injury crashes, that is, crashes in which no contact is made with an automobile. Moreover, there is bias in both police-reported and hospital-reported bicycle crash data because less severe injuries are reported and treated less frequently.

The study compared the information that city cops use, from the Statewide Integrated Traffic Records System (SWITRS), with records from San Francisco General Hospital, "the only trauma center for the city and county of San Francisco." Police reported 3,717 bicycle injuries from 2000 to 2009, and SF General reported 2,504 bicycle injuries during the same period, and "55% of bicycle injuries treated at SFGH were not associated with a police report." Which means that cycling accidents in this city have been under-reported by more than 50% (The MTA's Collision Reports rely on SWITRS and the SF Police Department.)

This problem with the numbers is not new. The Bicycle Plan's Framework document discussed it back in 2004:

The collision data presented in this chapter...does not include the many unreported bicycle collisions believed to occur in San Francisco...For the last several years, the San Francisco Department of Public Health has been working on an injury data linkage project using hospital admission data. Currently, San Francisco General Hospital (SFGH) is not obligated to report bicycle injuries to the SFPD. This is left up to the injured parties. EMS (ambulance services) is supposed to report bicycle injuries, but many are not reported (page 6-12, San Francisco Bicycle Plan: Policy Framework).

Odd that this never got done after all these years. Why? A possible explanation: If accurate data on cycling accidents in the city is gathered, it would confirm what critics like me are saying---that riding a bike in the city is a lot more dangerous than either City Hall or the Bicycle Coalition admits. That would also show that the city's aggressive promotion of cycling---encouraging even children to ride bikes---is irresponsible.

And the study found that treating cycling accidents between 2000 and 2009 cost the city $36.4 million.

The Centers for Disease Control tells us this is a national problem:

While only 1% of all trips taken in the U.S. are by bicycle, bicyclists face a higher risk of crash-related injury and deaths than occupants of motor vehicles do. In 2010 in the U.S., almost 800 bicyclists were killed and there were an estimated 515,000 emergency department visits due to bicycle-related injuries. Data from 2005 show fatal and non-fatal crash-related injuries to bicyclists resulted in lifetime medical costs and productivity losses of $5 billion.

No post about the NY Times and cycling would be complete without citing its story on another danger for serious cyclists.


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