Wednesday, August 17, 2011

Is it Crazy to Ride without a Helmet?

IN a provincial court last Friday morning, Vancouver resident Ron van der Eerden was defending his right to ride a bike without a helmet. Many people have concluded that Mr. van der Eerden is a loon. Yet a surprising fact is that, in a recent poll of British doctors, conducted by the British Medical Association, 68% agreed with him that helmets should not be compulsory for cyclists.

What can account for such craziness -- among doctors of all people?

To begin to find an answer, let’s ask a simple question. Compare an average person who cycles for transport, riding about 300 hours per year, with a typical motorist, also driving about 300 hours per year. Who is at greater risk of injury and death?

Answer: the motorist. This may be surprising, but it is a fact. While certain risks are very slightly higher for the cyclist, namely the risks from road accidents and air pollution, these increases are massively outweighed by lower risks of cardiovascular disease, cancer and diabetes, among other risks. A study published just this week in the British Medical Journal found that the risk-reductions of cycling (in Barcelona) compared with driving outweigh the risk increases by a factor of 77. Other studies have estimated the cost-benefit ratio at 20, or as little as 7, but no study has found that driving is safer. Cycling is far safer than driving.

This is something to bear in mind when thinking that someone is crazy to ride a bike without a helmet. If you’re an average Canadian, then that cyclist’s risk of death and injury is far lower than yours. Who is the crazy one here?

These studies take no account of whether a bicycle helmet is worn or not, since it makes very little difference. To see why, we can describe the situation with some rough, but reasonably accurate, numbers. Let’s compare two people, Chris and Mike. Chris cycles for an hour, while Mike drives his car for an hour. As a result, Chris’s life expectancy is reduced by about 5 minutes, due to the risk of death in a road accident. Mike’s life expectancy is also reduced by about 5 minutes, for the same reason. However, exercise is known to increase life expectancy, so Chris gains about 100 minutes in life expectancy from that. Overall, Chris gains 95 minutes, and Mike loses 5 minutes. Now, what about the helmet? A head injury is the sole cause of death in about 30% of cyclist deaths, and in the recent scientific literature helmets are estimated to prevent about 10-30% of such injuries. Hence wearing a bike helmet might reduce Chris’s chance of death by 3-10%, corresponding to an increase in life expectancy (per hour of cycling) of 9-30 seconds. In comparison with the general gain of 95 minutes, from cycling itself, the further gain of a few seconds from wearing a helmet is trivial.

Looking at these figures, it is little wonder that helmet laws, wherever they have been introduced, have had no noticeable impact on the rates of cyclist injury and death. And that the safest countries to cycle in are those where almost no one wears a helmet. Helmets are a non-issue for cycling safety.

There is also something perverse about fining someone for taking a personal risk, when the majority who take much larger risks are not fined. Given the clear fact that cycling (helmeted or otherwise) is far safer than driving a car, why are cyclists fined? As shown above, leaving one’s helmet at home costs a cyclist a few seconds of life expectancy, per hour in the saddle. If that same cyclist chose instead to drive a car for that hour, he or she would miss out on some 95 minutes of added life expectancy. The law guides us toward the more dangerous action. We should also remember the “second-hand risk” in driving a motor vehicle, i.e. the risk imposed on third parties. Driving for an hour costs other people a total of about 5 minutes of life expectancy as well. The law apparently prefers us to put others at risk rather than exposing ourselves to a much smaller risk.

Now, one might argue of course that even a small gain is a gain, and so wearing a helmet still a smart thing to do. At the same time, however, it’s not something to get worked up over. And it certainly isn’t a matter for legislation.