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07 May 2004
There's an intriguing graph in the latest issue of A to B, in which the number of fatalities per billion cycle/kilometers (effectively, the individual risk of death per cyclist, corrected for distance) is plotted against the average cycle distance per person per day. Fatalities increase very rapidly with decreasing cycle distance, with the UK falling somewhere near the bottom of the curve, with an average cycle distance per person of about 0.25 km/day. What this means is that as people cycle less, the risk of fatality for the remaining stalwarts increases sharply.
The theory is that this is due to drivers becoming more vigilant and careful about cyclists when they are common, which seems like a plausible explanation. In fact, there is apparently a power law (proposed by a Mr. Sneed in 1949) that suggests that the risk of collision with cars is as follows1:
where n is the number of cyclists or pedestrians.
The graph was in the context of the possible introduction of compulsory cycle helmetsâ€â€currently a very contentious issue for cyclists. The point is that in all countries where cycle helmets have been made compulsory, the number of cyclists has decreased. So on this evidence, the lower total number of fatalities might come with an increased risk of fatality to individuals. Given that many people are dubious about whether helmet use decreases or increases the severity of injury anyway, and that decreasing cycle use is likely to increase the burden on the NHS through increased obesity and cardiac problems, compelling people to wear helmets starts to look like a very bad idea. I do wear a helmet myself, but I'm not in favour of making everybody wear them.
1 You can learn things here, you know...
2
Timothy Brown: Yes, I saw an interesting documentary on just that subject a few years ago. And some people argue that bike helmets have exactly the same effect—people take more risks wearing one, and therefore their overall risk of injury doesn't change.
Keith: I'm sure that the experience of the rider is a factor too, along with the provisions made for cyclists like proper cycle paths (not the grudging 2 feet of pavement shared with pedestrians you get in this country), crossings over busy roads and so on. Each data point in the graph was the average for 14 European countries. The points aren't labelled, but I strongly suspect that the point at the far right of the graph at 2.5 km/person/day is the Netherlands. So provision for cyclists, experience and skill of cyclists and attitude of drivers are all confounded. Still, the point remains: the more cycling becomes an embedded part of the culture, the safer cyclists become.
3
I agree. Cycling in France, where it is commonplace, is much more enjoyable because the majority of road users there respect your right as a cyclist to be on the road. That is not the case here in the UK. I have often heard the view expressed that cyclists are some form of transport parasite, as they pay no tax on their vehicles. Too many road users here are also under the impression that the normal laws of physics do not apply to bicycles, that they travel at 0 mph, can stop or turn on a sixpence, and that passing one with one inch to spare at 70 mph causes no mental or physical turbulence to machine or rider.
Despite all this, bikes are still best.
by ThoughtBadger @ 09/05/2004 9:05 pm • Permalink •
4
I've thought that about cycling in Oxford - it's much nicer than in Norwich, say because drivers are more used to having to look out for cyclists all the time and the council provides actual facilities like cycle paths and bike racks for cyclists.
BTW, I'm getting an enourmous lag between pressing a key and the letter appearing here (useing Firefox 0.8).
5
ThoughtBadger: Hehe, I've had all of those ills visited on me. The other classic one is drivers vastly underestimating how fast one can travel on a bike, and therefore forcing you to slam on your brakes. I can hit 25mph quite easily downhill (more, if I'm feeling brave enough to take my hands off the brakes!), but people seem to assume you are going about 5mph.
Jo: It's slightly better, I suppose, though people still behave like idiots. Only yesterday, I saw a cyclist wiped out by an idiot passenger in a car flinging open his door without checking in the mirror. So perhaps it isn't better as such in Oxford, but slightly less bad (if that makes sense...)
1
This reminds me of the risk compensation hypothesis that argues that as there are more car safety measures (compulsory seatbelts, airbags) fatality rates stay constant because drivers drive faster, believing that their seatbelts etc will protect them in the event of an accident. So it's a zero-sum game. The bottom line being you need to think about (and study) the effects of safety technology on human factors.----- Couldn't there be other explanations here, such as cyclists who travel greater distances being more safety concious and doing things like wearing helmets, and hence experiencing fewer fatalities. On the other hand cyclists making shorter journeys are less experienced, and may be more at risk, particularly if they make their journeys in urban areas with heavy traffic, possibly a more dangerous environment for cyclists.
by Keith @ 08/05/2004 6:05 pm • Permalink •