Safety in numbers

What makes any bicycle safe on any street?

There is a theory in cycling literature that there is a safety in numbers effect for bicycles. This stems from the observation that where bicycles are not commonly found on streets, injury rates are higher, and where bicycles are commonly found on streets, injury rates are lower. Thus, goes the logic, if you get more people riding then all of them will be safer, presumably because drivers will know to watch for them.

I’ve always been suspicious of this theory, as it seems to confuse correlation and causality (although correlation can serve as a big causal hint). There are a lot of omitted variables that could both increase the number of bikes on the road and increase safety, like creating separated cycle tracks and instituting strict liability for drivers that hit cyclists and pedestrians. If people assess, correctly, that the infrastructure and legal system protects them, they’re both more likely to ride and they’re more likely to be safe, but increasing the number of bikes on the road wasn’t really what increased safety. If people jumped on bikes without that infrastructure or legal protection, I’m not sure they’d see the same effects.

This is part of the kindergarten bicycle crew at Rosa Parks each morning. I also feel safer when I join their impromptu bike train.

I thought of this last weekend when I was taking my daughter to her ballet class and suddenly found myself in a pack of over a dozen lycra-clad road cyclists on a major street. There were too many of us to stay in the bike lane, and so the fastest riders moved left into the car lane. Not all these cyclists were riding together—they came and went in small clusters—but everyone in the group was watching out for each other, and signaled to other riders (including me) when to move around turning cars and hazards in the street. Thanks, lycra-clad roadie guys!

I listened to them chat as we rode along. It was a pleasant ride, and I realized I did actually feel safer in a big group of cyclists. I knew someone would warn me if there were any obvious dangers in the road, and cars hung back rather than rushing to pass. That was very different from the same trip the week before, and from my ride home along the same route. Maybe there’s something to the safety in numbers theory after all.