Thursday, May 20, 2010

How safe is bike-commuting?

There are 1.25 fatalities for every 100,000,000 miles driven in a car. That doesn't seem like much, but if you travel 20,000 miles per year for 50 years it works out to a better than 1% chance that you will die in a car crash.

The statistics for bicycling are less complete, but such as they are they suggest that the rate per mile is about ten times as high compared to driving. To keep calculations simple let's just call it 10 fatalities per 100,000,000 miles.

Call me chicken, but this is alarming. Applying the statistics directly to my own situation, I ride upwards of 5,000 miles per year, giving me odds of 1:20,000 of dying this year while biking. Over a 20-year career that's a one-in-a-thousand chance of getting killed. Compare this to other risky activities:

  • Skydiving (per jump): 1:100,000
  • Killed by lightning (lifetime): 1:100,000
  • Plane crash (per trip): 1:1,000,000

The EPA, when assessing the risk of pollution levels, typically sets one in a million as unacceptably high. I'm comfortable with a one-in-a million risk; one in a thousand, not so much.

So how can I go about mitigating this risk? Quite a lot, I believe. What I see on the road convinces me that there is a lot of opportunity for bicyclists to improve their own chance for survival. To be honest, I'm astonished at the foolhardiness of many bikers. Here is just a small sample of behavior I've seen:

  • Crossing a busy intersection without checking whether car traffic is aware of you. I actually saw someone get hit crossing 65th this way, and I've seen several close calls on Stone Way. How hard is it to look left and right?
  • This one's similar: going straight through an intersection without looking for oncoming left-turners, or right-turners coming up behind you. At least one recent fatality in Seattle was caused by this situation. It's not much comfort to claim that the car was at fault.
  • Riding on unsuitable roads, such as Aurora Avenue North (which also happened to be the location of the above-mentioned fatality).
  • Riding at night in dark clothing with no lights. As a car driver with aging eyesight, I can assure you this renders you practically invisible.

I maintain that simply by taking common-sense precautions, the risk of accident can be dropped substantially. Statistics back this up. For example, one blogger has assembled data showing that young, inexperienced cyclists incur accidents at greater than ten times the rate of experienced cyclists.

But even experienced cyclists take risks that I myself avoid, so I believe in my case the risk is lower still. I know I've annoyed many a bicyclist with my cautious riding on the Burke-Gilman trail. Because of poor visibility I slow nearly to a stop at 70th and 65th to make sure no one's coming; I won't cross in front of a car until I make eye contact with the driver and have been given a clear signal to cross, particularly at high-traffic crossings like Blakely.

Recently I've been looking for the best route between Fremont and the Interbay Golf Course on Magnolia. My first attempt took me over an unacceptably steep hill. On my second attempt I tried a route that crossed the Ballard bridge, taking me within a few blocks of my destination, only to find that the pedestrian walkway on the other side didn't continue along 15th NW. My only options were to follow the safe route away from my destination, or to ride on the street. One look at the street convinced me to bail. I ended up taking a 15-minute detour just to avoid the traffic. Finally on my third try I found a suitable route that was pleasant, direct, and safe.

I have the added advantage that nearly 90% of my commute trip is along the Burke-Gilman trail, away from auto traffic entirely except for the street crossings. Cautious riding, experience, and a favorable route combine to reduce my personal risk to perhaps as low as 1:100,000 lifetime, I estimate.

That's still not one in a million, but it's almost certainly lower than the risk I would incur driving to work instead. Yet one more reason to ride!