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Thursday, February 10, 2011

No-Spin Zones - Is pedaling in traffic dangerous? (via The Daily)


1 comments:

tcristy said...

Time for the scientist to weigh in. Firstly, always read the original paper if possible, journalists regularly misreport or over-sensationallize.
http://injuryprevention.bmj.com/content/early/2011/02/02/ip.2010.028696.full.pdf?sid=a2ed422a-9dbe-409a-b762-40e0ffbcedc6

In this case, The Daily says streets are 28 times more dangerous that separate paths, which is totally incorrect. When six paths were compared with eight street segments in the same area of Montreal, five had higher risk on the street and three had higher risk on the paths. Only three of the comparisons were statistically significant. When averaged together, the paths were 28% safer (not times as the Daily article says, percent).

But its more complicated than that. They did not use the streets the paths run along for the comparison, but other refrence streets. They looked at car crash rates to determine how dangerous the reference streets are to the streets the bike paths are on. On average, they came out the same but the average hides the real story. Two of the reference streets were much more dangerous than the bike path streets - one 10x more dangerous and one 5x more dangerous. Those two streets are two of the three values were the bike path tested safer and showed the highest difference between path and street. Eliminate those two outliers and the whole study falls apart. There would be no difference in safety or it might actually tilt the other way.

The only thing they really succeeded in proving is that streets that are more dangerous for cars are also more dangerous for bikes, so it might be best to stay off them. Whether you take a light traffic street or path makes no difference.

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