Social damage and accident effects of the bicycle helmet law

The following analysis was prepared by C.F.CLARKE — Author of Safer Cycling 1995 Edition.

After more than 10 years of helmet research and promotion, there are still many aspects of their use that need to be quantified and social effects which are yet to be considered.

For example:

This article highlights a few of the social effects that are of obvious concern and lists expected benefits and potential disadvantages of helmet usage. Consideration is given to the time scale of expected benefits and disadvantages and this may assist individuals in estimating the likely worth of a helmet to themselves.

Social damage

Analysis of some of the social effects caused by either helmet promotion or mandatory usage shows how public wellbeing can be damaged.

Accident effects of helmets

There is also concern regarding the effects helmets have on accidents and injuries. Listing both the benefits and disadvantages of helmets illustrates the variables involved and their complexity.

Helmet benefits

Given a direct or near direct impact of low to moderate velocity to the skull portion of the head, a helmet should provide some protection and surface damage to the skull could be avoided or reduced. Most standard tests involve direct impacts so the benefits are predicable provided other bodily injuries are not so severe as to cause death. In the event of a high velocity impact to the head, helmets seem unlikely to provide much protection.

Helmet disadvantages

The number of impacts to the head of a helmeted cyclist will generally be higher than for a non-helmet wearer. This is due in part to the larger size of the helmet compared to the bare head.

What may be a near miss for a bare head could have an impact force of 70% of a direct impact for a helmet wearer. Diagram A shows a profile of a helmet and bare head with a table of the forces involved at lines/angles of impact. Research7 and boxing experience indicate side impacts to the head may cause more brain damage than frontal impacts. Helmet wearing appears to almost double the side forces involved.

Research is necessary to determine the influence of helmet wearing on the number of impacts (probably up by more than 40%) and to equate the benefits from shell and foam thickness to the disadvantages of extra impacts. Evidence of frontal impacting is gained through general accident data which shows children have double the number of facial injuries compared to skull injuries8.

Research is also needed to identify the most common impact zones on helmets.9, 10. There is no doubt that helmeted cyclists have more impacts than those who are non-helmeted11, 12. With the brain having a soft constituency that can be damaged by rotational forces and by impacting on the inside of the skull, any additional impacts need to be considered very carefully. In the absence of skull fractures, rotational shearing forces on the brain rather than direct impact compression may cause the most brain injuries36 (see eMedicine for more detail).

Cyclists have been known to take high risks when helmeted, possibly believing a helmet will offer significant protection. This results in the number of accidents increasing. Studies indicate boys have about twice the accident rate of girls per distance travelled13 and generally it is thought that boys take more risks, resulting in more accidents.

One OECD report14 found that by wearing florescent coloured caps, children showed indications of increased risk-taking. So-called safety helmets misleadingly claim to reduce the risk of head injuries by 85%15, so it is hardly surprising some children may take more risks when cycling. According to J. Franklin6 , "TRL reported that a significant minority of children (believed to be 19%) cycle less carefully when wearing a helmet".

Most cyclist head injuries are facial injuries. This is why the 85% claim is misleading. In the majority of cases, helmets offer little if any protection to the face. When helmet promoters make misleading claims such as this, they are coercing cyclists into a false sense of security which leads to more accidents.

Helmets can be subject to high g forces, according to research16 which measured the accelerations involved to the head when a cyclist experiences major shocks from potholes in the road. It found peak acceleration of up to 10g forces could occur at deep potholes (the 10g can also be arrived at by calculation of the vertical component of acceleration). This indicates forces up to 10 times the weight of a helmet can be suddenly applied to the head and at a time when maintaining balance may be most difficult. The direction of the forces is said to be random, so at times these forces will contribute to a cyclist losing his/her balance.

Helmet weights vary from about 200 to 600 grams with no weight limit specified in the British Standards. The public may believe the heavier type of helmet is best. However, these heavier helmets are more likely to increase the risk of having an accident and no warning is given.

In addition to the three main disadvantages of extra impacts to the helmet/head, higher risk-taking behaviour by some cyclists and sudden helmet forces that can affect balance and riding stability, there is a range of other minor disadvantages.

For example, when braking hard any extra mass on the head contributes slightly to the rider going over the handlebars17. Furthermore, extra mass can contribute to increased fatigue. Wind noise can occur due to the strapping or hole configurations and patterns in helmets and this may slightly detract from the ability to detect approaching traffic. Southampton University research31 indicates that helmets can modify the pattern of sound reaching the ears.

Helmets can increase scalp temperature18 and this may affect concentration and alertness, as well as causing increased sweating. The risk of neck injuries may increase because helmets take extra impacts compared to a bare head and more stress will be applied to the neck. Helmet strapping may also lead to more neck injuries due to the strapping or buckles.

A young child may even wear a helmet back to front by mistake or the helmet may sometimes be worn toward the front of the head, and peripheral vision may be affected by the strapping.

Rotational damage of the brain inside the skull is probably more important than direct impacts. However, no standard tests for rotational effects are involved in helmets being approved19. If a cyclist falls off at 15mph (6.7m/sec) wearing a soft-shell helmet with an effective diameter of 250mm, and the helmet grips the road, the head could rotate at the equivalent of 530rpm. Near misses to the bare head in Diagram A could result in rotational forces on impact for helmeted cyclists, causing brain damage.

General disadvantages include costs that vary from about £10 to £80, inconvenience (time spent choosing a suitable helmet and replacing it, carrying a helmet when shopping or securing it when not cycling, storage facilities at schools, effects on hair styles, etc), comfort aspects and possibly being distracted when riding. Helmets may need replacing after a few years because the inner polystyrene degrades in ultra-violet light and after prolonged exposure to the sun, becoming brittle and ineffective in a heavy fall38.

People with arthritic conditions or symptoms may find the fastenings difficult to manage and may also be affected by the extra weight of a helmet contributing to discomfort when cycling. There are probably more than 200 approved helmet makes to choose from worldwide. Of 24 tested by Which37, only 9 passed all tests. Therefore, the public cannot be confident about helmets and none can be classed as safe due to the lack of appropriate research. Holes in helmets can even act as fly, bee and wasp catchers.

In summary, there are numerous effects causing social harm including the discouragement of cycling1,20,21,22,23, expelling children from school, reduced compensation to cyclists, the issuing of fines, possible imprisonment due to non-payment of fines, using police time and resources which may detract from enforcing speed limits and other important road safety measures, a less active society with a consequent health benefit loss, less public cycling with a reduced incentive to provide quality cycling facilities, a loss of civil liberty32, and an increased rate of accident involvement11,27, 33.

Helmet use appears to have only one advantage compared to more than 20 possible or likely disadvantages.

Death and injury

Roughly 12 million people cycle in the United Kingdom during any given year and about 200 die annually. On average, 12 million years of cycling equates to 200 deaths - or one death per 60,000 years of average cycling. In Australia, about 80% of cyclists wear helmets and about 80% die helmeted, meaning helmets have little effect on saving lives. Rodgers reported in 1988 24 that helmets are significantly associated with an increased fatality rate.

Research data varies regarding how effective helmets may be. Excessive claims of 85% protection have been made15. Other research suggests about 30%27 and for children in Melbourne a 10% or lower rate appeared to be the result26. If 10,000 head injuries per year occurred in the U.K. from the 12 million people who cycle and helmets provided 30% protection, this would be an average one head injury saved per 4000 years of average cycling (12 million divided by 10000 = 1200 average years, divided by 0.3 = 4000 years).

If 60 years is the approximate average lifetime, then once in 66 lifetimes a helmet would save you from a serious head injury. The problem with this prediction is that helmet wearing increases the number of accidents and head impacts... therefore the benefit of once in 66 lifetimes may be overtaken by any slight increase in the number of accidents.

This is supported by Australian research. D. Robinson27 showed data in 1996 relating to accidents and surveys for children in New South Wales. Overall, the accident rate increased by an amazing 68% relative to cycle usage after the NSW mandatory helmet law was introduced. Having a legal requirement has reduced the safety of children as well as discouraging them from cycling... overall, a disastrous outcome.

Comparing the benefits and disadvantages

If helmets had no disadvantages, the average cyclist could expect a helmet to save his/her life about once in 10,000 lifetimes of average cycling and prevent a serious head injury about once every 66 lifetimes. Given the wide range of disadvantages, many of which cannot be avoided, it is probable that they are more significant overall than relatively infrequent advantages. During an average lifetime of cycling, the helmet effect on balance, hard braking and reduced caution will increase the probability of helmeted cyclists having more accidents.

Helmet promoters are unwilling to accept that helmet wearing increases accidents and the number of head impacts because helmets are larger than the skull. However, the fundamental science governing cycling and impacts prevails.

Many medical reports compare helmeted and non-helmeted data but fail to account adequately for the rate of accident involvement and cannot include near misses for non-helmeted cyclists. As a result, the comparisons are fundamentally weak. Convenience, comfort, cost and freedom of choice are also very important considerations for some people in their appreciation of cycling.

Furthermore, reduced compensation because a cyclist was not wearing a helmet demonstrates a complete lack of subject knowledge by the legal profession and shows how Britain's Highway Code advice to wear a helmet is also at fault.


The promotion of helmet wearing leads to some people being discouraged from cycling because of social pressures used by helmet advocates. Having a legal requirement has resulted in a sharp fall in the number cycling. Moderate exercise like cycling has many health benefits and also helps reduce pollution caused by vehicular traffic29.

Life years gained through cycling have been calculated to exceed life years lost in cycle fatalities by a factor of 20 to 1 (Hillman BMA report unpublished30). Therefore, helmet promotion which has discouraged cycling has resulted in social harm. The evidence available suggests cyclists are generally safer not wearing a helmet if all aspects are considered.

This seems to apply to children even more than adults, possibly because children have larger heads in relation to body size and adding a helmet worsens their balance. Children cycle experimentally - up and down kerbs, for example - incurring higher g forces than normal, and helmet wearing contributes to them losing control and falling off more often. In addition, children have been told helmets could save their life and some may be inclined to thus take slightly more risks. One report asked cyclists in a roadside survey11 if they had hit their heads in the previous 18 months and indicated that helmet wearers were 7 times more likely to have done so than non-helmeted cyclists.

The analysis of impacts comparing helmeted to bare heads indicates a basic problem of helmet safety will remain regardless of how well helmets are designed. Given all the disadvantages helmets can produce, they should not be recommended as a safety product for cycling and a warning of their danger needs to be given explaining why they will in most cases actually reduce the overall safety of the wearer.

Some racing helmets made with aerodynamic features including a point at the rear may add to brain injuries if the point impacts before a cyclist lands on his/her back. This is yet another helmet danger that needs investigating.

The EFC34 wrote that "the evidence from Australia and New Zealand suggests that wearing of helmets might even make cycling more dangerous". The evidence presented in this paper supports the EFC view and explains why helmet effects make cycling more dangerous.

An interesting ruling in the Australian Capital Territory Supreme Court interpreted their helmet law in such a way that any cyclist who believes on reasonable grounds that wearing a helmet would increase the risk or severity of injuries need not wear one35. There are reasonable safety and other grounds for deciding not to wear a helmet. Consequently, there should not be any reduction in civil litigation compensation due to a cyclist not wearing a helmet.

Parents may wish their children not to wear helmets to avoid the possible increase in accident risk, to eliminate the possibility of hanging and asphyxiation, or to minimise the number of impacts to the head in falls or collisions. They may also wish to encourage their children to cycle for its health and enjoyment benefits without the inconveniences of helmet wearing.

Trading Standards and British Standards do not provide a balanced account for cycle helmets and the public is generally subject to misleading pro-helmet propaganda. Cycling groups could help by discussing the topic at conferences, not advertising helmets in their publications and by promoting the research necessary to gain a full scientific appraisal of the topic. Civil liberty groups could also take sufficient interest to be aware of the social damage occurring due to helmet promotion and act to safeguard the public's fundamental freedom of choice.



Helmeted:- (sin Q)2 (sin Q x cos Q)

Angle Q sin cos Y force frontal (sin Q)2 X force sidewards (sin Q x cos Q)
10 0.1736 0.9848 0.0301 0.1709
20 0.3420 0.9396 0.1169 0.3213
30 0.5000 0.8660 0.2500 0.4300
40 0.6427 0.7660 0.4130 0.4923
50 0.7660 0.6427 0.5867 0.4923
60 0.8660 0.5000 0.7500 0.4330
70 0.9396 0.3430 0.8828 0.3213
80 0.9848 0.1736 0.9698 0.1709
90 1.0000 0.0000 1.0000 0.0000
Totals 4.9999 2.8350

Non-helmeted:- Corresponding impacts for above, angles below 45 degrees would be misses or near misses

50 - 27.5 0.4617 0.8870 0.2132 0.4095
60 - 51 0.7771 0.6293 0.6039 0.4890
70 - 65 0.9063 0.4226 0.8213 0.3830
80 - 77 0.9743 0.2249 0.9493 0.2191
90 - 90 1.0000 0.0000 1.0000 0.0000
Totals 3.5872 1.5006

For helmeted impacts, there could be increased forces in the Y direction (frontal) of 39% and increased forces of 89% in the X direction (sidewards).

Experiments by the Defence Evaluation and Research Agency found that impacts to the side of the head (X direction) can cause more brain damage than impacts in the Y direction. Some of the forces may be reduced by helmets spreading the load or by having a cushioning effect but helmets are unsupported on their side edges and may deflect, thus not providing a great deal of protection.

In the case of a 45 degree impact to the helmet, a force of more than 70% of a full direct impact could be transmitted to the helmet. Without a helmet, a near miss could occur with no forces applied to the head whatsoever.

Colin Clarke provides more data on increased injury risk in Comparing impacts for helmeted and non-helmeted (Word, 108kb).


1) Road and Traffic Authority Survey, New South Wales 1992, Australia.

2) Times Educational Supplement, 27 March 1998, "Jailed for not wearing a bike helmet".

3) "Expelled from school" Derby U.K. reported by GMTV, 2 Dec 1997.

4) Accidents involving Cyclists, published by Holt & Turners Solicitors, Preston U.K.

5) Cycle Touring and Campaigning, October/November 1997.

6) J Franklin, "The effectiveness of cycle helmets". CTC publication 1999. (PDF file 152k)

7) Reported on Tomorrows World, Defence Evaluation Research Agency information.

8) Hazard No 6, Victorian Injury Surveillance System publication, Australia.

9) M William, "The protective performance of bicycles’ helmets in accidents", Accid Anal & Prev Vol 23 No 2/3. Pp119-131,1991.

10) T. Smith, "Evaluation and replication of impacts damage to bicycle helmets". Accid Anal & Prev Vol 26, No6, 795-802,1994.

11) R.C. Wasserman, "Bicyclists, Helmets and Head Injuries: A Rider —Based Study of Helmet Use and Effectiveness". AJPH September 1988, Vol 78, No 9, pp 1220-21.

12) M.M Dorsch, "Do bicycle safety helmets reduce severity of head injury in real crashes". Accid. Anal. & Prev. Vol 19, pp183-190, 1990.

13) Victorian Cycling Strategy 1990, Accident Statistics for Australia.

14) O.E.C.D. Report, Safety of Vulnerable Road User. 1998.

15) Thompson, "A Case-Control Study of the effectiveness of Bicycle Safety Helmets". New England Journal of Medicine, May 1989.

16) Mathieson and Coin, "Bicycle Helmet Vibrations and Relation to Helmet Dislodgement during normal road use". Paper No 23, Bikesafe Conference, Newcastle, Australia, 1986.

17) Whitt and Wilson, Bicycling Science, MIT Press, Chapter 8, Braking Effects.

18) J Mathieson, "Helmet ventilation tested", Australian Cyclist.

19) N J Mills and A Gilchrist, "The effectiveness of foams in bicycle and motorcycle helmets", Accid Anal and Prev, Vol 23 No 2/3, pp 153-163, 1991.

20) Sheperd R, "Helmet law discourages cycling", Australian Cyclist, Oct 1991.

21) Vicroads, Report IR90, "Initial effects of mandatory bicycle helmet wearing legislation". July 1991

22) N.C. Smith and F.W. Milthorpe, "An observational survey of law compliance and helmet wearing by bicyclists in New South Wales —1993", Road and Traffic Authority 1993.

23) C.F. Finch, L. Heiman, and D. Neiger, "Bicycle use and helmet wearing rates in Melbourne", Monash University, Accident Research Centre report No 45, February 1993.

24) G. B. Rodgers, "Reducing bicycle accidents: a re-evaluation of the impacts of the CPSC bicycle standard and helmet use", Journal of Product Liability, Vol 11, 1988, pp307-317.

25) M.D. Sage, F.J. Cairns, T.D. Koelmeyer and W.M.I. Smeeton, "Fatal injuries to bicycle riders in Auckland", NZ Med J, 1985, Vol 98, No793, pp1073-1074, 1985.

26) Personal communication, Victorian Injury Surveillance System accident data.

27) Robinson D, "Head injuries and bicycle helmet laws" Accid Anal and Prev 28, 4,1996, p 463-75

28) Accident data from Federal Office of Road Safety, Canberra, Australia

29) B.M.A., "Cycling Towards Health and Safety", 1992

30) Personal communication, Dr M Hillman, author "Cycle Helmets — the case for and against", 1993.

31) G J Beynon, "An investigation into the effect of cycling helmets on the wearer’s ability to localise sounds" Project report, ref 154-231, Acoustics and Vibration, Eng & Applied Science, University of Southampton.

32) Curnow, Road Rules OK? Self—Protection and Social Damage, Australian Current Affairs Bulletin April/May 1998.

33) B Pitt, S Thomas, J Nixon, R Clark, D Battistutta, C Action, Trends in head injuries amongst child bicyclists. BMJ 1994,308, p177.

34) European Cyclists Federation, "Improving Bicycle Safety without making helmet-use compulsory. 1998.

35) Van Schaik v Neuhause 1 May 1996.

36) Holbourn, A.H.S., Mechanics of head injuries, The Lancet, 2, 338-441, 1943, B. Curnow 1999.

37) "Get a head start" Which /October 1998, p 28-31.

38) "Keep a lib on it" On Your Bike/May 2000.

Colin Clarke studied mechanical engineering at Huddersfield University and was a graduate member of the Institution of Engineers Australia, having worked in the aircraft design, petrochemical and heavy engineering industries, among others. Colin qualified in 1970 as a British Cycling Federation coach. He has cycled for more than 40 years covering approximately 300,000km in more than 20 countries. He has worked as a road safety instructor teaching children how to ride bicycles safely and is currently a National Councillor for the Cyclist's Touring Club, Britain's leading cycling organisation. Having been a racing cyclist for several years, Colin now campaigns for better cycling infrastructure in the United Kingdom.

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