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What evidence is there that cycle helmets save lives?

There is no direct evidence that the wearing of cycle helmets has led to fewer deaths amongst cyclists. Most research into cycle helmets has not included cyclist fatalities.

The premise that helmets save lives is by extrapolation from research that has suggested that helmets might reduce injuries to the head. As most fatalities involve head injury (this applies to all major external causes of violent death, not especially cycling), the reasoning is that by reducing injuries to the head, cycle helmets can lead to fewer cyclist deaths.

Whole population data

Whole population statistics for cycling fatalities do not support the above hypothesis.

Long-term analyses of fatalities in Canada [8], New Zealand [9] and USA [10] [11] show no helmet benefit; indeed, one study [11] suggests helmeted cyclists are more likely to be killed. Although fatality rates have generally declined, cyclists have fared no better than pedestrians. In Great Britain, too, there has been no discernible improvement in fatality trends relative to pedestrians as helmets have become more common [12] [13] .

In New South Wales, Australia in the three years following the introduction of its helmet law, 80% of cyclists killed and 80% of those seriously injured wore helmets at the time [3] [4]. These proportions are almost identical to wearing rates in street surveys (85% and 83% for adults in 1992 and 1993 respectively; 76% and 74% for children [3] [5]), suggesting that helmets had little effect on the likelihood of fatal or serious injury.

In Western Australia where bicycle helmets have been mandatory for all ages since July 1992, the annual cyclist death toll from 1987 to 1991 (pre-law) averaged 7.6 fatalities per year. From 1993 to 1997 (post-law) it was 6.4 fatalities per year, representing a 16% reduction [6]. Government cycling surveys show cycling declined in Western Australia by approximately 30% during the 1990s following mandatory helmet law enforcement [7]. Thus the increase in helmet wearing as a result of the law did not reduce fatalities relative to cycle use and may have led to an increase.

Comparing Australia-wide fatalities in 1988 (before any helmet law) with 1994 (when all states had enforced laws and about 80% helmet wearing), cyclist, pedestrian and all road user deaths fell by 35%, 36% and 38% respectively. Head injury deaths fell by 30%, 38% and 42%. Despite very high helmet use, the reductions for cyclists were less than for the other road users [17]. The differences are much greater still if the considerable fall in cycle use as a result of the helmet laws is taken into account.

NEISS data from the US shows that over the latest 15-year sample period, head injury was a factor is fewer than one half (45%) of bicyclist deaths [20].

Local research

Specific research into fatalities in Sheffield, UK [1] has shown that even if head injuries were eliminated completely, at least 50% of cyclist deaths would still occur. Most fatalities involve multiple injuries and head injury is not the sole cause of death. The experience of a solicitor specialising in cyclist injuries [14] supports the view that deaths solely due to head injury are unusual. Furthermore, fatal head injuries typically involve rotational forces, which cycle helmets do not mitigate and may even make more likely [2].

Cyclist deaths were also investigated in Auckland, New Zealand [15]. 16 of 19 non-helmeted cyclists died from mulitple injuries, so helmets would not have changed the outcome. Only one cyclist died of head injuries in a bike-only crash, the most likely situation for a helmet to help. That cyclist died despite wearing a helmet and a fall at moderate speed. The researchers concluded: "This study indicates that the compulsory wearing of suitable safety helmets by cyclists is unlikely to lead to a great reduction in fatal injuries, despite their enthusiastic advocacy".

A study of cyclist crashes in Brisbane, Australia concluded that helmets would prevent very few fatalities [16]. All deaths were caused through collisions between a bicycle and a motor vehicle. For 13 of the 14 cyclists who died, there was no indication that a helmet might have made any difference. The authors were very concerned about brain damage from rotational injuries and recommended developing a new test to measure the sliding impact friction of helmets.

Inherent limitations of helmets

In inner London, 58% of cyclist fatalities were caused by collisions with heavy good vehicles, as were 30% of those in outer London [18]. The idea that a lightweight polystyrene helmet could be of significant benefit in such circumstances is unrealistic and has to be balanced against the potential for a helmeted head to incur more impacts due to its increased size compared with a bare head.

The tragic case of 4 helmeted cyclists killed by a car travelling at 50 mph demonstrates that cyclists often die in impacts too severe for a helmet to help [19].

Conclusions

Despite the considerable effort that has been put into research about cycle helmets, there is no real-world evidence that helmets have ever resulted in the net saving of even a single life. However, if helmets were actually effective, then many more pedestrian and motor vehicle occupant lives could be expected to be saved if these groups wore helmets.

References
[1] Kennedy A The pattern of injury in fatal pedal cycle accidents and the possible benefits of cycle helmets 1996. British Journal of Sports Medicine: 1996 Jun;30(2):130-3
[2] see: Cycle helmets and rotational injuries.
[3] Robinson DL. Head injuries and bicycle helmet laws. Accident Analysis & Prevention, 1996 Jul;28(4):463-75.
[4] Road Traffic Accidents in New South Wales, 1992, 1993, 1994. Roads and Traffic Authority of New South Wales.
[5] Smith NC, Milthorpe FW. An observational study of law compliance and helmet wearing by bicyclists in New South Wales 1993. Roads and Traffic Authority NSW, 1993.
[6] Meuleners LB, Gavin AL, Cercarelli LR, Hendrie D. Bicycle Crashes and Injuries in Western Australia 1987-2000 RR131; Injury Research Centre, School of Population Health, The University of Western Australia, November 2003.
See also: Cyclist injury data before and after helmet law in Western Australia.
[7] Main Roads WA official surveys of cyclist numbers, primarily those relating to the major Narrows and Causeway bridge locations.
See also: Bike numbers in Western Australia: Government surveys.
[8] Burdett AJ. Cyclist fatality trends in Canada, 1975 - 2002 .
[9] Burdett AJ. Cyclist fatality trends in New Zealand, 1976 to 2002.
[10] Kunich TH. Latest CPSC Helmet Standard and US Fatality Trends.
[11] Rodgers GB. Reducing Bicycle Accidents: A Reevaluation of the Impacts of the CPSC Bicycle Standard and Helmet Use. Journal of Products Liability, 1988,11:307-317.
[12] see: Casualty trends in Great Britain.
[13] Hewson PJ. Cycle helmets and road casualties in the UK. Traffic Injury Prevention, 2005;6(2):127-134.
[14] see: A solicitor's experience.
[15] Sage MD, Cairns FJ, Koelmeyer TD, Smeeton WMI. Fatal injuries to bicycle riders in Auckland. NZ Med J, Vol 98, No793, pp1073-1074, 1985.
[16] Corner JP, Whitney CW, O'Rourke N, Morgan De. Motorcycle and bicycle protective helmets: requirements resulting from a post crash study and experimental research. Federal Office of Road Safety, Report CR55.
[17] Curnow WJ. The Cochrane Collaboration and bicycle helmets. Accident Analysis & Prevention, 2005;37(3):569-573.
[18] Gilbert K, McCarthy M. Deaths of cyclists in London 1985-92: the hazards of road traffic. BMJ, BMJ;1994:308(6943):1534-7.
[19] Four cyclists killed in car crash. BBC News on-line, 8 January 2006.
[20] see: NEISS data on bicyclist injuries.

Page last updated 30th August 2006