Better to be careful: the safety value of bicycle helmets seems a no-brainer, but guess again.

The bicycle helmet debate was back on the front pages this fall, given a British study that showed wearing helmets is more dangerous than going without. Compulsory helmet-law advocates have since been on the defensive, and that's good, not simply because helmets fail to do their jobs--saving lives and reducing injuries--but also because they have some unexpected consequences.

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Proponents of compulsory helmet laws seem to suggest that Canada is suffering an epidemic of cycling injuries and deaths. Yet Transport Canada statistics have remained constant at roughly 78 cycling deaths yearly since 1991; given about 18 million Canadian cyclists, this yields a fatality rate of roughly one in 231,000. There were almost 200 fatalities back in 1975, but the decline from the 1970s to the 1990s started well before helmet laws were widespread. Pedestrian deaths also dropped over that period, suggesting that factors like improved trauma care were the real contributors.

The same is true in other countries. Although helmet use has increased in the U.S., there is no reliable evidence that this has reduced head injuries or fatalities. G.B. Rodgers looked at 8 million cases over 15 years (Journal of Products Liability) and found "no evidence that hard shell helmets have reduced the head injury and fatality rates." Indeed, "the bicycle-related fatality rate is positively and significantly correlated with increased helmet use." The New York Times reported 73,750 head injuries from cycling in 2000, compared with 66,820 in 1991. And children's head injuries have returned to 1991 levels, though fewer kids now ride bikes.

Australian data, comparing fatalities from 1988 and 1994, shows cyclist and pedestrian fatalities declining at the same rate. But the introduction of helmet laws brought about a 25 per cent decline in cycling, so the apparent drop in cycling fatalities may represent a proportionate increase. So Dorothy Robinson of the University of New England concluded that Australian helmet-wearing caused no statistically significant decline in head injuries.

Perhaps this is why countries like the Netherlands, with one of the world's highest cycling rates--25 per cent of all trips--has one of the lowest rates of helmet use.

Why do the figures suggest that helmeted cyclists are not safer, but may be at even greater risk? First, the real issue is preventing cyclist deaths. Virtually all their deaths and most of their acute brain injuries are caused by collisions with cars, where helmets are virtually useless. John Franklin, with the U.K. government task force on cycle training standards, notes that current standards require helmets to provide protection at an impact velocity of only 20 kilometres per hour, offering little protection against autos. Helmets are tested only on their ability to resist linear force, not rotational forces, though most brain injuries result from rotational forces. And U.K. Consumers Association research indicates that most helmets fail even these minimal standards. A 1998 study found that 14 out of 24 helmets tested failed the shock absorption standard; and only two of the 24 met the more rigourous "Snell absorption standard."

But a further reason why helmets don't work is found in what Queen's University psychologist Gerry Wilde calls "safety compensation." The introduction of a safety feature actually encourages, rather than reduces, risk-taking, because individuals feel safer. Bringing in anti-lock brakes during the 1990s, intended to reduce accidents, resulted in more accidents, since drivers trusted that their brakes would be "safer." Similarly, studies of helmet-wearing children have found them suffering more crashes than unprotected children. Even adults seem to ride faster and take greater risks when wearing helmets. And the risk compensation factor appears to govern the behaviour of motorists in relation to cyclists--as shown by the U.K. study setting off the latest round of debate. It found that British drivers allowed more room when passing cyclists without helmets, compared to cyclists with them.

Helmet use fails to reduce cycling deaths or injuries, but succeeds in making cyclists feel safer and take more risks. It also makes cycling much less attractive for many, so its net health benefits are significantly reduced. Rather than worrying whether cyclists wear helmets, perhaps the nanny state should provide more cycle paths.