Is bike-share the safest way to cycle?

Abbott recants and embraces a tax on carbon - "if you want to put a price on carbon why not just do it with a simple tax?"! The Melbourne Urbanist is not politically partisan, but gives credit to any politician who shows this sort of courage! (wow, the things they can do these days with a bit of smoke and a few mirrors! Remarkable)

According to this story, riders of share-bikes are involved in fewer accidents and sustain fewer injuries than cyclists who ride their own bikes. The author provides an impressive array of examples.

In Paris, Velib riders account for a third of all bike trips but are involved in only a quarter of all bike crashes. In London, the first 4.5 million trips on the new “Boris bikes” resulted in no serious injuries, whereas the same number of trips on personal bikes injured 12 people.  The situation in Boston DC is similar:

In its first seven months of operation, Capital Bikeshare users made 330,000 trips. In that time, seven crashes of any kind were reported, and none involved serious injuries. In comparison, there were 338 cyclist injuries and fatalities overall in 2010, according to the District Department of Transportation, with an estimated 28,400 trips per weekday, 5,000 of which take place on Capital Bikeshare bikes.

So it seems likely that Melbourne Bike Share’s unloved Bixis are at least a safer way to travel than ordinary bicycles. The implication of the story is that upright bicycles may be safer than the racers and mountain bikes we’re used to in Australia. That might sound plausible on first hearing, but I’m not so sure.

What strikes me straight up about these numbers is that relative trip rates don’t provide a valid basis for comparison. The only sensible measure is “accidents per km” because it indicates the relative exposure to potential accidents. Share-bike riders pay more the longer they rent the bike, so they have an incentive to take relatively short trips. On the other hand, I think it’s very likely personal riders travel longer distances – e.g. for commuting or leisure – and accordingly have greater exposure to potential accidents.

That doesn’t “disprove” the claim that share-bikes are safer than ordinary bikes, it just says the quoted statistics don’t tell us if they are or they aren’t. But for the sake of argument, let’s suppose share-bikes are safer, even if the difference is less dramatic than the quoted numbers suggest (intuitively, I suspect they actually are a bit safer on a per km basis). But if so, what is the underlying reason? Is it some intrinsic quality of share-bikes? After all, they’re heavier and therefore slower than ordinary bikes so that might explain it. Another reason might be their more upright riding position, which makes them more visible to motorists.

These explanations could have some role, but I think there are more obvious reasons why share-bikes might have a lower accident rate (if in fact they actually do). Read the rest of this entry »