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June 23, 2005

Collision Course II

Last week, I wrote a post detailing how much car crashes cost.  An alert reader asked some followup questions about how to reduce his risk:

Does a decrease in vehicle-miles translate to a decrease in injuries? Am I relatively safer on my bike? On the bus?

Here are some quick answers.  First:  the more you drive, the greater your chance of getting in a crash.  See, for example, this chart from a Victoria Transport Policy Institute analysis of car crashes in British Columbia:
The relationship is pretty close to linear.  So if you want to decrease your crash risk, the most obvious strategy is to arrange your life so you can drive less, if you can.  Of course, some roads are riskier than others -- and rural two-lane highways are among the riskiest.  Congested urban roads and streets tend to have more crashes per mile driven than average, but fewer fatalities -- slower speeds make crashes less deadly.  Which may be one reason why the risk of dying in a car crash is higher at the urban fringe than in center cities or inner-ring suburbs, and why sprawling cities are more dangerous than compact ones.

Next:  If you want to be safer, take transit.  Measured per passenger-mile, transit buses and commuter rail are about as safe as you can hope for; buses seem to be more than 10 times safer than cars for their occupants, while commuter rail is about 80 times safer.  (But both are more dangerous than cars for other occupants of the roads.)  I wish I could say that biking would make you safer, but it doesn't seem to; mile for mile, biking is about 10 times deadlier than driving. Exercise benefits may partially offset the increased crash risk.

It's a shame that biking is so risky in the US.  Biking fatalities are down, of course -- they fell by 27% between 1975 and 2001 -- but mostly because of a steep drop in cycling by children.  But in Germany, the exact opposite has happened:  the number of bike trips doubled between 1975 and 2000, while the number of bike fatalities dropped by 64%. The difference, according to some researchers, is that public policy in Germany has emphasized bike and pedestrian safety -- including infrastructure, traffic calming, traffic education, and traffic regulations -- while policies in the US tend to emphasize fast travel by car.

One side note--although traffic fatality rates in the US are among the highest in the developed world, US drivers aren't particularly unsafe, nor are the roads we drive on.  Measured per mile, our fatality risk is about average.  The real difference is that we drive much more than our counterparts in other nations--and all else being equal, more driving means more car crashes.

Posted by ClarkWD | Permalink


Just a quick note: we must remember that bicycle crash statistics are skewed in relation to car fatalities in a number of ways:

1) Car drivers are adults (or almost) and have training (not enough or there wouldn't be so many crashes). Kids as young as 5 can master the bicycle but aren't developmentally able to process information well enough to avoid traffic. Adult, experienced cyclists have very few crashes.
2) Crash rates need to be compared on a per trip basis, not a per mile basis as bike trips are shorter than average car trips.
3) Roads are typically hostile environments encouraging speeds beyond the capabilities of humans except under favorable circumstances (witness the 40,000 deaths a year in the US). They are even more so for pedestrians and cyclists. It is a crime that national "standards" allow for this kind of carnage.
4) in Portland, Oregon we have seen crash numbers remain constant while cycling increased 5-fold in the last ten years (mainly due to substantial completion of a system of bike faciities) meaning that crash rates have fallen significantly proving the value of bike lanes and other treatments for both increasing safety and use of cycles.

Finally, if your city is unsafe to cycle in its the result of a deliberate decision by city traffic engineers and public works departments to make it unsafe. We know what works: cities that don't provide for safe cycling are negligent and short sighted.

Posted by: rex Burkholder | Jun 27, 2005 9:46:44 PM

Rex -
That's really helpful context. The same thing is true of pedestrians. The raw statistics suggest that walking is dangerous (even if measured per trip, rather than per mile). But most of the pedestrian fatalities are among children, the elderly, and the intoxicated. So walking for transportation, if you're a sober adult in good health, is a lot safer than the raw statistics would suggest.

Where can I get bicycle crash & trip data for Portland?

By the way, I've been in a few bicycle scrapes myself; I've been tapped by a car (nothing but road rash, thankfully), and fallen all by myself a few times on slick pavement. And one of those falls left me in a cast for a few months, and unable to run for over a year. I'm a bit of a klutz, of course, but my experience may have colored my opinion about the inherent safety of biking.

Posted by: Clark Williams-Derry | Jun 28, 2005 10:37:12 AM

for info on bike crash statistics and ridership try Roger Geller at Portland Office of Transportation roger.geller@pdxtrans.org

Posted by: rex Burkholder | Jun 29, 2005 12:08:04 PM

Regarding biking in Germany: According to recent changes in German laws, if you hit a bicycle rider while driving a car, you are automatically guilty and responsible regardless whether you broke any traffic rules or not. This law is strictly enforced in those cases where the bicycle rider is a child (under the age of 18).

Regarding bicycling in the US, one factor rarely mentioned yet contributing to the many bicycle accidents, is the very poor condition of many roads especially in cities. Large potholes and other holes especially those due to rainwater runoff into the sewer system represent major risks to bicycle riders in the US. The popularity of SUV's is in my opinion partly due to the very poor condition of our roads.

The most pleasent country to bicycle in is Netherland. They have special roads for bicycles ONLY paralell to regular roads. Few years ago, while on a vacation trip in Netherland, I enjoyed very much the safety of their bicycle road network. Even in cities they have special lanes which are reseved for the bicycle traffic. Unfortunately, we will never see such things in the US simply because there are not enough bicycles in this country. Whether that will change after the peak oil transition, I do not know.

I work in Newark (NJ)- 5 miles away from Jersey City where I live. I would love to use my bicycle in order to get to work. Unfortunately, this is impossible since all roads linking these two cities are are highways with very dense car traffic. Riding a bicycle on these roads is illegal and extremely dangerous. Twenty years ago I lived in Maryland in an apartment complex which you could reach only by car via a highway. It was impossible to reach that place by foot unless you took the risk of crossing a highway by foot. The US infrastructure is designed with the idea that everybody drives a car. Bicycles are a nuisance.

Posted by: Robert Sczech | Jul 4, 2005 7:06:10 AM

Some interesting assumptions in the post and comments that many of us cyclist hold, but which at least one cyclist questions, concerning such things as the dangers of cycling vs driving and the safety of dedicated bike lanes. A very provocative examination of these assumptions and studies that have looked at them:
One tidbit:
"Although a mile of driving is ten times safer than a mile of cycling, a mile of urban driving is ten times more likely to kill a pedestrian than such a mile cycled." The author goes on further to note that the benefits of cycling outweigh the risks by a factor of 20-1, as determined by a British long term health study. So your claim that "Exercise benefits may partially offset the increased crash risk," would probably be more accurately stated: Exercise benefits significantly offset the increased crash risk.

Posted by: tricky coyote | Jan 17, 2006 2:12:53 AM