The Telegraph took recently released bike accident data from Transport for London to create an interesting map showing the locations of bike crashes in London. The accompanying text says this map shows “the most dangerous areas for cycling in London,” repeating the error made by many other efforts to map bicycle crash data.
The map at the Telegraph’s website is well done and contains useful information showing where cyclists get hit by cars, but does it actually show how dangerous these locations are? Or does it merely show where people in London are likely to ride their bikes? Without exposure data, it’s difficult to tell. This is a common but understandable oversight, since exposure data is usually not available.
If we take the absolute number of cyclist fatalities as a proxy for road safety, then the M25 ring road and its intersections with the various other motorways around London are the safest place to ride your bike in London. I don’t know London, but I suspect the real reason we don’t see cyclist fatalities on these high speed motorways is because nobody rides on them, and nobody rides on them because they’re likely not safe.
Can maps like this be used to improve cyclist safety? Certainly. The Telegraph story points out, for example, that TfL plans to increase the speed limit on Blackfriar Bridge. Their crash map shows many bicycle crashes in the vicinity. Crazy thought, I know, but maybe TfL can make changes that benefit the large number of cyclists in the vicinity?
In a related story using the same data, we find that eight of the 12 cyclist deaths in London between August 2010 and July 2011 involved a large truck. I don’t know the ratio of cars to trucks in London, but that seems like an awfully high ratio. According to the Telegraph, cyclists involved in a crash are 78 times more likely to die beneath the wheels of a ‘heavy goods vehicle’ than otherwise. The London Cycling Campaign — a membership group that advocates for cyclist safety and access in London — would like improved safety standards for truck drivers throughout London.
Thank you to John Burn-Murdoch, who crunched the TFL numbers for the Telegraph.