The secret to Team GB’s cycling dominance at London 2012 was not the only cycle-related debate to arise out of the Olympics. The sad news that a 28 year-old cyclist had died in a collision with a bus outside the Olympic park reignited the controversy over cycling safety, and in particular whether cycle helmets should be compulsory.

The fatality, which was the tenth cycling fatality on London’s roads so far this year, prompted gold medalist and recent Tour de France winner, Bradley Wiggins, to enter the debate. At a press conference following his gold medal time-trial win, Wiggins said that making it illegal to cycle without a helmet would make the roads safer “because ultimately, if you get knocked off and you ain’t got a helmet on, then how can you kind of argue”. Wiggins later clarified his comments via twitter: “Just to confirm I haven’t called for helmets to be made the law as reports suggest. I suggested it may be the way to go to give cyclists more protection legally.”

On 20 June 2010, another Olympic medalist, British rower James Cracknell, was hit on the back of the head, whilst cycling, by a fuel truck travelling at 75mph along the Arizona desert. He credits his cycle helmet for saving his life: “Despite a massive crack down the back of my head (25 staples took care of that) and significant bleeding to the frontal lobes of my brain, I am here to tell the tale. There is only one reason for that: my cycle helmet.”

However whilst cyclists who have been involved in an accident might perceive that their helmet prevented more serious injury or even death, the evidence is not clear-cut. For example, the Bicycle Helmet Research Foundation reports that “in high impact crashes, such as most that involve motor vehicles or fixed objects like concrete barriers and lamp posts, the forces can be so great that a helmet will compress and break in around 1/1000th of a second. The absorption of the initial forces during this very short period of time is unlikely to make a sufficient difference to the likelihood of serious injury or death.”

A large proportion of cycling injuries are crush injuries to the body and limbs for which clearly a helmet affords no protection. In the days after the cyclist fatality outside the Olympic park, his family made it clear that he was in fact wearing a helmet. He was killed by a vehicle turning left and suffered devastating bodily injuries.

Opponents of compulsory cycle helmet laws frequently cite the example of The Netherlands. Despite being widely regarded as the safest country in the world for cycling, only an estimated 0.5% of Dutch cyclists wear helmets. The Dutch cycling safety record is often attributed to better awareness and understanding of cyclists and cycling infrastructure. Cycling safety advocates argue that the focus on the helmet debate detracts attention from the need for safer road layouts and infrastructure which would do far more to prevent cycling injuries and fatalities.

London mayor, Boris Johnson, has also recently joined the debate on cycling safety, commenting, “I have to say that in countries where they have made them compulsory, it hasn’t always necessarily been good for cycling.” He was referring to evidence from countries which have implemented mandatory helmet laws that the laws discourage cycling. For example, in the state of Western Australia a mandatory helmet law came into force in 1992 and post-law enforcement statistics indicate that there was a sharp decline in cycle numbers. Critics of compulsory cycle helmets laws would argue that the health benefits of promoting cycling in cultures with rising obesity outweigh any benefits, unproven in any event, of mandatory helmet requirements.

Some critics go further still and argue that cycle helmets actually make the roads a more dangerous place for cyclists because they alter motorists’ behaviour. For example, a 2006 study of 2,300 vehicles found that drivers tended to pass notably closer to cyclist wearing helmets.

Despite there currently being no legal requirement to wear helmets, cyclists pursing a personal injury compensation claim as a result of a road traffic accident can face a deduction of up to 25% of their damages if they were not wearing a helmet. This is on the basis that “as it is accepted that the wearing of helmets may afford protection in some circumstances it must follow that a cyclist of ordinary prudence would wear one.” However, there will only be a deduction in compensation for failing to wear a helmet if it would have reduced or prevented injury.

In the case of Smith v Finch there was no deduction from the cyclist’s compensation for contributory fault on the basis that, the court found, a helmet would have made no difference. In that case, the claimant relied on a motorcycle safety expert who gave evidence that a helmet would only have provided protection for the claimant if he had struck the ground at a lower speed and also that the site of the head injury was below the lower edge of the helmet. As such, the claimant’s evidence was that in the particular circumstances of his case a helmet would not have provided the necessary protection to avoid his injuries, and that was accepted by the court.

This is based on the same principle of contributory fault as applied to passengers not wearing seatbelts. But defendants usually find it much harder to show that a helmet would have prevented or reduced injury than with a seatbelt.