Cycle Helmets

Cycle helmets are designed to be effective “particularly [in] the most common accidents that do not involve a collision with another vehicle, often simply falls or tumbles over the handlebars.¹” They are not designed to offer any useful protection in the event of a collision with a motor vehicle.

Despite this, helmets are often incorrectly promoted by both public bodies and individuals as providing useful protection in the event of a collision with a motor vehicle. Without knowing the wider debate around cycling helmets, a user will feel safer whilst riding wearing a helmet, and they will appear less vulnerable to other road users who have been subjected to the same promotion. The increased perception of safety both by the user of a helmet and other road users who encounter a helmet user changes the behaviour of both parties, through a phenomenon known as risk compensation². A helmet-wearing cyclist may adjust their behaviour to compensate for their increased perceived safety. More importantly, it has been shown³ that risk compensation behaviour on the part of other road users leads to the average passing distance given by other road users decreasing, increasing the likelihood of a collision in which the helmet will provide no safety benefit to the wearer.

Promoting helmets as a road safety measure is ignoring the bull in the China shop. The source of danger on our roads is the speed and volume of motorised traffic, and the behaviour of motorists. Helmets are a useful means for the motoring lobby to shift the focus away from this by placing the burden of protection (a demonstrably inadequate protective measure at that) on the victims themselves, rather than by moderating the speeds, number and behaviour of their members who are the source of the danger to cyclists⁴.

Heavily promoting helmets, and especially making them compulsory with legislation suppresses cycling. In Australia and New Zealand cycling numbers fell significantly when helmets became compulsory. Head injury numbers in Australia actually increased after helmets became mandatory despite the number of cyclists falling significantly⁵. Other injuries increased, believed to be linked to the drop in cyclist numbers, motorists’ behaviour being altered by the infrequency with which they found themselves encountering a cyclist on the road after helmets became mandatory. Heavy promotion of helmets, or making them compulsory overstates the fairly minimal risks of injury involved in cycling (comparable to walking), making cycling seem like a less attractive or viable transport option for both existing and potential cyclists.

A thorough review of the evidence

Ben Goldacre, Wellcome research fellow in epidemiology and David Spiegelhalter, Winton professor for the public understanding of risk, have conducted a thorough review of the literature relating to risks and benefits of bicycle helmets in an editorial for the BMJ⁷

They say, science tries to answer 2 main questions, both of which they claim are methodologically challenging and contentious:
1. At a societal level, “what is the effect of a public health policy that requires or promotes helmets?”
2. At an individual level, “what is the effect of wearing a helmet?”.

They cite a paper by Dennis (bmj) which investigated the effect of Canadian helmet legislation on hospital admission for cycling head injuries, which they found “seems to have been minimal.

They say, “This finding of “no benefit” is superficially hard to reconcile with case-control studies, many of which have shown that people wearing helmets are less likely to have a head injury.3 Such findings suggest that, for individuals, helmets confer a benefit.” but they also point to methodological shortcomings of studies, which have many possible confounds.

Importantly they also talk about “second round effects” of introducing helmet legislation. Studies show regular cyclists live longer because the health effects of cycling outweigh the risks. So, looking at overall public health, if a helmet law puts people off cycling, it is doing them harm in other ways, due to inactivity.

They go on, “Standing over all this methodological complexity is a layer of politics, culture, and psychology. Supporters of helmets often tell vivid stories about someone they knew, or heard of, who was apparently saved from severe head injury by a helmet. Risks and benefits may be exaggerated or discounted depending on the emotional response to the idea of a helmet”

And, “It is certainly true that in many countries, such as Denmark and the Netherlands, cyclists have low injury rates, even though rates of cycling are high and almost no cyclists wear helmets. This seems to be achieved through interventions such as good infrastructure; stronger legislation to protect cyclists; and a culture of cycling as a popular, routine, non-sporty, non-risky behaviour.”

They conclude that the “current uncertainty about any benefit from helmet wearing or promotion is unlikely to be substantially reduced by further research…. The enduring popularity of helmets as a proposed major intervention for increased road safety may therefore lie not with their direct benefits—which seem too modest to capture compared with other strategies—but more with the cultural, psychological, and political aspects of popular debate around risk.”

"A helmet saved my life"

One type of anecdote frequently told when discussing cycle hemets follows the general form of “A helmet saved my/a friend’s life.” These anecdotes often describe the helmet split in two, with its owner convinced that it saved their life. Anecdotes and evidence are not the same thing, with no control experiment (where all variables other than whether or not the rider was wearing a helmet are left unchanged) it is impossible to state with any confidence whether or not the helmet had made a difference, or to appropriately quantify any difference it may have made. In scientific research it is also standard practice to repeat an experiment and the associated control experiments several times to ensure that the results observed are representative of real life rather than a freak occurrence. When considering road safety issues in particular, it is important to consider the effects of risk compensation, as discussed above.

Additionally there are safety concerns attached to wearing a helmet, including increased risk of rotational brain injury which can be further exacerbated by the interaction between the air vents on a helmet and irregularities in the road surface leading to an increased risk of neck injuries⁶. These effects obscured by the general acceptance (even amongst helmet advocates) that there are limits to the protection a helmet can provide; if a helmet-wearing cyclist is injured in a collision, the injuries they sustain may merely be uncritically disregarded as being “less substantial than if they had been without a helmet,” when in fact they may have been exacerbated or even caused by the presence of a helmet.

It is also important to consider that plenty of cyclists survive collisions, accidents and other incidents whilst not wearing a helmet. Unlike the sensational “Life-saving helmet,” stories which are commonplace whenever there is a discussion regarding helmets, people who survive collisions, accidents and other incidents whilst not wearing a helmet rarely link their survival to the fact that they were not wearing a helmet.

¹ Transport Research Laboratory: The Potential for Cycle Helmets to Prevent Injury

² Munich Taxi Cab ABS Risk Compensation Experiment

³ Dr Ian Walker’s Investigation into the link between perceived safety of cyclists and passing distance given by other road users

⁴ Australian Helmet-camera study shows motorists to blame in majority of incidents involving cyclists and motorists

⁵ The effect of the Australian mandatory cycle helmet law on cycling rates and head injury rates

⁶ The effect of cycle helmets on rotational brain injuries and neck injuries

⁷ Bicycle Helmets and the Law (BMJ, 2013)