Below is a summary of the various studies concerning helmet and helmet law effectiveness. We’ll be adding to this list regularly.
There is little doubt that helmets are good at what they are designed to do – limiting linear deceleration from low-speed impacts. The AS/NZS2063 standards for bike helmets require a helmet dropped from 1.5m to have an impact deceleration of less than 250g. That’s the equivalent of hitting the ground at a bit under 20 km/hr. Helmets are also good at limiting some lacerations, abrasions and other surface injuries – that’s about all.
What helmets aren’t good at is protecting the head during high-speed impacts – AS/NZS2063 explicitly states that bike helmets are not designed for use on motorcycles. There is no research to our knowledge that examines the efficacy of bike helmets in high-speed impacts and, based on the physics behind AS/NZS2063, it seems that a helmet would offer little protection from a collision with a motor vehicle travelling at 60 km/hr.
Deaths of cyclists due to road crashes (2006), ATSB Road Safety Report, Australian Transport Safety Bureau, Canberra.
Helmet Law Effectiveness
While helmets might be great at limiting head injury during low-speed impacts, there is little evidence to show that mandatory helmet laws make cycling safer. On the contrary, helmet laws may actually make cycling in general more dangerous.
No clear evidence from countries that have enforced the wearing of helmets
Safety in Numbers
One of the most important safety issues for cycling is the number of cyclists. Numerous studies from around the world have shown a strong inverse relationship between the number of cyclists and the risk of cycling. Put simply, doubling the number of cyclists makes cycling 30-50% safer, as fewer people drive and those motorists adapt their behaviour to the increased number of cyclists.
Helmet Laws and Cycling Levels
Whenever helmet laws have been introduced, cycling levels have decreased significantly. There are a number of reasons for this: cycling is perceived to be more dangerous if the law requires helmets to be worn; cycling, especially everyday/utility cycling, becomes less convenient if a helmet has to be worn and then carried around; some people find helmets uncomfortable, more so in hotter climates; some people don’t like ‘helmet hair’.
Mandatory helmet laws have also been widely recognised as being primarily responsible for the poor performance of the cycle-share schemes in Brisbane and Melbourne. Mexico City and Israel both repealed their helmet laws and their cycle-share schemes have performed better ever since.
Active Commuting to School and Cognitive Performance in Adolescents: The AVENA Study‘, Arch Pediatr Adolesc Med, Dec 2010