I dug this up for another discussion, and found I'd made a significant error - 30M x 1K = 30B, not 3B! I've revised it below. The bottom line is that, if my assumptions are correct, or at least if they more-or-less cancel out, cycling is about 10x as dangerous as driving per mile,
NOT 100x as I'd originally calculated!
Courier, that's a great talk ... but the speaker unintentionally points out just how risky cycling is per mile - or maybe not, as I crunch some numbers. 40,000 car deaths/year in the US, but over, what, 200,000,000 drivers x 15,000 miles/year/driver? (This is just an estimate on my part.) That's 2 x 10^8 x 1.5 x 10^4 = 3 x 10^12 miles (i.e. 3 trillion miles) driven annually in the US. 3 x 10^12 miles/4 x 10^4 traffic deaths = 0.75 x 10^8 miles driven/traffic death = 7.5 x 10^7 miles/traffic death. That's 75 million miles driven per traffic death. Can that be right? Someone please check my numbers. In any case, following the same logic, let's say there are 30 million cyclists in the US, each averaging 1000 miles/year. That's 30 billion (3 x 10^10) cycling miles total per year. 3 x 10^10 cycling miles/4 x 10^3 cycling deaths = 0.75 x 10^7 cycling miles/death. That's a cycling death per every 7.5M miles ridden. So by my rough estimates, cycling is about 100 x more dangerous than driving per mile. And yet, I figure I've ridden perhaps 70,000 miles over the past 35 years of cycling as an adult. That's only about 1/100th of the 7.5M miles associated with a cycling fatality. So, cycling is relatively dangerous (compared to driving), but still quite safe in absolute terms. And perhaps I tip the odds in my favour a bit by wearing a helmet (I've wrecked two in crashes), a high-vis vest, using lights, having a mirror, and obeying the rules of the road. Furthermore, I enjoy really good health, due in part to the cycling. My odds of dying on the road are higher than that of a car driver, but my chances of dying from cardiovascular disease or cancer are lower than someone who doesn't exercise. Again, someone please check my numbers. I may be way off on how many drivers and cyclists there are in the US, and how much they drive. As well, the more cycle commuters there are, the fewer cars there are on the road, making things that much safer for cyclists.