Fact sheet

Bicycle helmets

Summary

Nearly one third of all cyclists in the Netherlands who are severely injured in a bicycle crash sustain head and/or brain injury. More than 800 cyclists per year sustain head and/or brain injury in a collision with a motor vehicle. In addition, more than 2500 cyclists per year suffer from head and/or brain injury after a crash or a fall not involving a motor vehicle (bicycle-only crash). In 86% of the cases the head injury of a cyclist is (also) brain injury. A bicycle helmet offers the best possible protection against head injury for impact speeds up to approximately 20 km/h. The use of a bicycle helmet reduces the risk of severe head injury by more than 65%. The more the impact speed exceeds 20 km/h , the more the protective effect of the helmet declines. SWOV has calculated that a mandatory bicycle helmet use for young children in the Netherlands can lead to annual savings of 5 road deaths and 140 serious road injuries. For older cyclists mandatory helmet use can lead to annual savings of also 5 road deaths and 220 serious road injuries. On the other hand, such a compulsory measure may reduce bicycle use, which could be negative for public health and the ambitions in the area of accessibility, liveability and sustainability.

This fact sheet presents a survey of the scientific facts about bicycle helmets. More general information about the safety of cyclists and possible measures can be found on the SWOV web page Bicycle.

Facts

How big is the problem of head injury among cyclists?

Nearly one third of all cyclists in the Netherlands who are severely injured in a bicycle crash, have head and/or brain injury. In bicycle crashes with a motor vehicle almost half the cyclists sustain head injury (47%); in bicycle crashes not involving a motor vehicle, this is the case for two in five cyclists (38%; Weijermars et al., 2014; See also SWOV Fact sheet Serious road injuries in the Netherlands.

Table 1 shows the numbers as well as the risks of head and/or brain injury among severely injured cyclists in the Netherlands, based on data from the National Medical Register (LBZ) 2010-2014. 'Head injury' in this table is brain injury in 86% of cases, the remaining 14% are head injuries without brain injury. Noteworthy is that the size of the risk coincides with the age of the cyclist. In bicycle crashes with a motor vehicle the risk (per distance travelled) of head and/or brain injury increases considerably from 75 years of age; in bicycle crashes without involvement of a motor vehicle, the risk of head and/or brain injury is particularly high for 0-5 year olds and for cyclists older than 75.

Table 1. Annual number of cyclists with serious head and/or brain injury (MAIS2+, as primary or secondary diagnosis, rounded to multiples of five), the percentage relative to all cyclists in that age group who have been admitted to hospital with serious injury (MAIS 2 +), and the number relative to the distance travelled by bicycle (Risk); for different age groups and calculated over the period 2010-2014 (sources: Dutch Hospital Data – LMR/LBZ; Statistics Netherlands – Study ‘Distances travelled in the Netherlands’).
 
How does the bicycle helmet protect against head injury?

A bicycle helmet ensures that in case of a fall from the bicycle the impact force on the head is absorbed and delayed and the force of an impact is spread over a broader area. The helmet also prevents the head from direct contact with the ground or an object. The bicycle helmet consists of a hard plastic exterior with an interior of polystyrene (styrofoam) and weighs about 250 grams.

Bicycle helmets that are sold within the European Union must comply with the European standards EN-1078 (helmets for adults) and EN-1080 (helmets for children). The difference is in the way the chin strap is attached to the helmet: children's helmets have a chin strap that snaps off in case the helmet snags, which prevents them from choking (Kemler et al., 2009). For the best result, it is important that the helmet fits properly and is fastened correctly. It is also important that the helmet is undamaged and not history of previous impacts.

To what impact speed does a helmet offer protection?

The bicycle helmet offers protection against head injury at impact speeds of up to about 20 km/h; that is the speed of a cyclist who rides slowly and then falls with his head on the street (De Baan, 2012). The more the impact speed exceeds 20 km/h,  the faster the protective effect of the helmet lessens.

According to the European standard the protective effect of bicycle helmets is tested at a speed of approximately 20 km/h on a flat surface (flat anvil) and 17 km/h on a surface that simulates a curb (curb anvil). These speeds are based on single-bicycle crashes,  leading to a fall from the bicycle. In crashes with a motor vehicle these speeds can be many times higher; in these cases it is less easy to calculate the degree of protection as the different forces that can result from the collision process are too unpredictable. The European standard for bicycle helmets, the standard the Dutch bicycle helmet must also comply with, is milder than the standards in for instance the United States and Australia.

Do bicycle helmets protect cyclists from (fatal) head injury?

Yes: according to three independent sources – biomechanical research, simulation research, and case‑control research – a bicycle helmet reduces the risk of head and/or brain injury in case of a crash or fall.

In biomechanical research bicycle helmets are tested in the laboratory on their shock-absorbing effect. In a test in which a head-shaped form  fell down a distance of one and a half metres it was estimated that the bicycle helmet reduced the risk of serious brain injury by almost 100% to about 10% (Cripton et al., 2014). The helmets that were tested, complied with the mandatory bicycle helmet standard in the US. This CPSC-standard uses slightly higher requirements than the European EN-1078-standard (see e.g. Mizuno et al. (2014) for a comparison of test conditions of different standards).

In simulation research, both the physical forces that act on the head and the possible protective effect of a helmet are simulated in a model. Based on computer simulations of three types of bicycle crashes, Fahlstedt et al. (2016) established that a bicycle helmet could diminish the risk of concussion by more than 50% and the risk of a skull fracture by more than 90%. 

In case-control research the head or brain injury of cyclists who do or who do not wear a helmet is compared. The meta-analysis by Olivier & Creighton (2016) is the most recent and extensive overview of so-called case-control studies of the protective effect of a bicycle helmet. Olivier & Creighton estimate that the risk of severe head injury decreased by 69% and that of fatal head injury by 65%. The estimates in this meta-analysis are based on 40 case-control studies. In these studies the injuries of a total of 64,000 cycling casualties with and without helmet were compared.

Case-control studies on bicycle helmets have been criticized, because the statistical analysis would lead to an overestimation of the protective effect. Also the frequently used control group (cyclists in the emergency department of a hospital with other injuries than head injury) may differ on important aspects? – such as cycling behaviour and distance travelled by bicycle – from the cases (cyclists with a head wound; see e.g. Zeegers, 2015). Although these points are justifiable to some extent, we do not expect that they can explain the total effect found by the case-control studies. Besides, most of the case-control studies were performed in the United States, Canada and Australia, where the traffic infrastructure is different from that in Netherlands. Bicycle crashes may therefore also be different, and this can potentially affect the estimation of the protective effect of bicycle helmets. No case-control studies of the protective effect of bicycle helmets have as yet been executed in the Netherlands.

Does a bicycle helmet also have adverse effects?

Some studies show adverse effects of bicycle helmets on crash involvement. Due to 'behavioural adaptation' cyclists may feel safer wearing a bicycle helmet and as a result they may show more risky cycling behaviour. It is unclear what this could mean for the safety effects of helmet wearing; several studies contradict each other.

Robinson (2006) indicates that cyclists wearing a helmet show riskier cycling behaviour or encounter more risky driver behaviour. It is not clear to what extent this is actually the case in practice. The study by Robinson is too limited. Walker (2007) found that drivers showed more risky behaviour towards a cyclist wearing a helmet: when overtaking they were closer to the cyclist with a helmet than to the cyclist without a helmet. As a possible explanation he mentions that the driver sees helmeted cyclists as more skilled than cyclists not using a helmet, and therefore uses smaller safety margins. Phillips et al. (2011) found indications for (unsafe) behavioural adaptation by experienced helmet users: they experienced less risk while wearing a helmet and they cycled faster than when they did not wear a helmet during the same ride. Cycling with or without a helmet had no effect on the risk or cycling speed of inexperienced helmet users.

On the basis of a questionnaire study in Norway, Fyhri et al. (2012) conclude that cyclists do not show more risky cycling behaviour because of the helmet, but that the causal relationship is reversed: just because these cyclists tend to cycle in a risky manner, they use protective equipment such as the bicycle helmet. Other studies indicate that young helmet wearing cyclists take no additional risks (see Hagel et al., 2006). Elvik (2013) concludes that there is insufficient clarity on this subject.

Finally, bicycle helmets are occasionally assumed to increase the risk of neck injury (Elvik, 2013), but the meta-analysis by Olivier & Creighton (2016) found no evidence for this assumption (see also under the heading Do bicycle helmets protect against (fatal) head injury among cyclists?).

How often are bicycle helmets used in the Netherlands?

We do not know how many cyclists wear a helmet in Netherlands and how often. Generally, bicycle helmets are not a familiar sight in the Netherlands. From the 1990s onward, bicycle helmet use has increased, especially children’s helmets (Goldenbeld et al., 2003). Besides, a large majority of the touring and sport cyclists wears a bicycle helmet: 96% of touring and sport cyclists indicate to always wear a bicycle helmet (Wijlhuizen & Van Gent 2014).

Which developments can affect the effectiveness of bicycle helmets?

New developments in the field of helmet design and technology may contribute to more safety and protection of cyclists. Several manufacturers, for example, develop ‘intelligent' helmets. These helmets indicate, using led signals, when the rider brakes and in which direction he turns (Lumos-bicycle helmet). The intelligent helmet can also warn a cyclist if it detects a vehicle in the blind corner of the cyclist (Classon-bicycle helmet). Efforts are also made to create a better protection against 'rotational' (sideways) forces to the head in a crash (KU Leuven and UZ Leuven, presented on 5 July 2016; and MIPS [i]).

Another development is the airbag for cyclists, which is worn around the neck as a kind of collar (the ' Hövding-airbag ', see Hövding, 2016). In the event of a crash the airbag is activated, which fixes the neck and protects the head. The Hövding-airbag is not subject to the European standard for conventional bicycle helmets (see also under the heading How does the bicycle helmet protect against head injury?). It distinguishes itself very positively in several helmet tests in Sweden (Folksam, 2015). Finally, there are also concrete proposals for new, better bicycle helmet tests (Bogerd et al., 2015).


[i] Multi-directional Impact Protection System – MIPS.

Is helmet use mandatory on a pedelec or a speed pedelec?

The Netherlands has no mandatory helmet use for the pedelec (pedal assistance up to 25 km/h), because this is considered a 'normal' bicycle. For the speed pedelec (pedal assistance to 45 km/h) mandatory helmet use applied from 1 January 2017. According to European regulations, the speed pedelec is since then categorized as a moped (until 1 January 2017 it was classified as a light moped). The speed pedelec helmet can be an 'ordinary' moped helmet that complies with the ECE22.05-standard, or it can be a helmet that meets the NTA8776:2016 standard which has been developed specifically for the speed-pedelec (Schepers et al., 2016). This helmet does have a number of specifications that differ from the 'regular' bicycle helmet (see Figure 1).

Figure 1. Differences in requirements for the standard bicycle helmet and the helmet for the speed pedelec (Source: Volkskrant, 11 August 2016).
What are the motives for wearing or not wearing a bicycle helmet?

The evaluation of the bicycle helmet campaign in the Dutch Province of Zeeland found that for both children and their parents the main motive for wearing a bicycle helmet is safety (Boele et al., 2016; Goldenbeld et al., 2016). The most frequently mentioned reason for children not to wear helmets, is that their peers do not wear bicycle helmet and that the parent does not want the child to stand out (Boele et al., 2016). Another reason for parents not to have their child wear a helmet, is that their child is careful and cycles safe enough, and that they find the route to school sufficiently safe. No studies are known into the motives of adults to wear or not wear a helmet.

There also is international research into the motives of children and students to wear or not to wear a bicycle helmet (see e.g: Lajunen, 2015; Pierce et al., 2014; Ross et al., 2010). As cycling culture and helmet use often differ from that in the Netherlands, it is not clear how these results may apply in the Dutch situation.

How effective are bicycle helmet campaigns?

Promotion campaigns can effectuate an increase in bicycle helmet use. Towner et al. (2002) mention the results of 19 studies on such bicycle helmet campaigns. Most of them were carried out in the United States and Canada and were specifically aimed at children. The studies showed different results, but the researchers conclude that promotion generally increases the helmet use, that the largest effect is achieved among young children and girls, and that especially discounts on the price contribute positively to the purchase and use of bicycle helmets.

The most recent large-scale campaign in the Netherlands (in the Province of Zeeland) also had a large effect, but only in the first year of the campaign (Boele et al., 2016). During the period 2010-2015, this bicycle helmet campaign ('Wanna look cool, wear a helmet!') distributed a total of 32 thousand free bike helmets to children aged 4-8 years; this was accompanied by educational and information activities (Boele et al., 2016). The purpose of this campaign was to encourage young children to voluntarily wear the bicycle helmet and thus to prevent head injury. In the first campaign year almost five times as many children (4-8 years) wore a bicycle helmet in Zeeland as before the campaign: an average increase of 3.3% to 15.7%. In the control area the bicycle helmet use did not change (almost 0%). The size of the behavioural effect was found to coincide with the intensity of the annual campaign activities.

What is the effect of campaigns on bicycle use?

Opponents expect that compulsory helmet use  or even encouraging helmet use will make cycling less popular. This will consequently lead to a negative health effect: fewer head injuries, but also a less fit population. Recent studies show that this effect of stimulating helmet use is probably very low. According to Danish research cycling behaviour of 19 out of 20 cyclists is  not influenced by information about cycling safety and bicycle helmets (Danish Road Safety Council, 2016). Also the evaluation of a bicycle helmet campaign in the province of Zeeland found no effect of the campaign on bicycle use (Boele et al., 2016). Moreover, children who usually or always wear a helmet, did not cycle less. In France voluntary helmet use increased from 7% in 2000 to 22% in 2010, while bicycle use remained equal during that period (Richard et al., 2013).

What are the effects of making the use of bicycle helmets mandatory?

Mandatory helmet use will increase helmet use and will protect more cyclists against head and/or brain injury in a bicycle crash. Yet there is almost no support for mandatory helmet use in the Netherlands, not even from traffic organisations (Aarts et al., 2014b). For specific target groups that run a slightly more risk in traffic, such as children and the elderly, SWOV has made an estimate of possible injury reductions due to mandatory helmet use. SWOV expects that a mandatory bicycle helmet for young children (0-11 years) in the Netherlands can lead to annual savings of 5 deaths and 140 serious road injuries. Mandatory helmet use for the elderly can lead to annual savings of 5 deaths and 220 serious road injuries (Aarts et al., 2014a).

A possible downside is that mandatory helmet use reduces bicycle use, which can be negative for public health. De Jong (2012) calculated that this outweighs the potential benefits of more bicycle safety. Sieg (2014) also concludes that bicycle helmet legislation for Germany leads to more costs than benefits. Newbold (2012), who extended the calculation model of De Jong, concludes that mandatory helmet use in the United States will indeed result in an improvement in public health.

Furthermore, Olivier et al. (2014; 2016) conclude that there is no convincing evidence that that bicycle helmet legislation would lead to less cycling. Berenbaum et al. (2015) conclude that there are mixed results about the effects of bicycle helmet legislation on bicycle use. Based on US data Kraemer (2016) concludes that helmet use among students increased due to  mandatory helmet use, whereas the evidence on the effects on bicycle use was ambiguous.

 

Publications and sources

Aarts, L.T., Eenink, R. & Weijermars, W. (2014a). Opschakelen naar meer verkeersveiligheid. Naar maximale verkeersveiligheid voor en door iedereen. R-2014-37. SWOV, Den Haag.

Aarts, L.T., Eenink, R.G., Weijermars, W.A.M. & Knapper, A. (2014b). Soms moet er iets gebeuren voor er iets gebeurt; Verkenning van mogelijkheden om de haalbaarheid van de verkeersveiligheidsdoelstellingen te vergroten. R-2014-37A. SWOV, Den Haag.

Bambach, M.R., Mitchell, R.J., Grzebieta, R.H. & Olivier, J. (2014). The effectiveness of helmets in bicycle collisions with motor vehicles: A case-control study. In: Accident Analysis & Prevention, vol. 53, p. 78-88.

Baan, D. de (2012). Fietshelmen bieden minder veiligheid dan we denken. Artikel geplaatst 29 februari 2012, op http://www.dirkdebaan.nl/verkeer-uitgelegd.html, bekeken 7 september 2016

Berenbaum, E., Ha, P., Keller-Olaman, S. & Manson, H. (2015). Impacts of mandatory bicycle helmet legislation. Ontario Agency for Health Protection and Promotion (Public Health Ontario), Queen's Printer for Ontario, Toronto.

Boele, M., Panneman, M., Adriaensens, L., Goldenbeld, Ch., et al. (2016). Fietshelmcampagne Coole kop, helm op! in Zeeland; Evaluatie van de effecten. SWOV/VeiligheidNL, Den Haag/Amsterdam.

Bogerd, C.P., Annaheim, S., Halldin, P., Houtenbos, M., et al. (2015). Helmet optimization in Europe: The final report of COST Action TU1101 / HOPE. COST Action TU1101 / HOPE collaboration. European Cooperation in Science and Technology COST, Brussels.

Cripton, P.A., Dressler, D.M., Stuart, C.A., Dennison, C.R. et al. (2014). Bicycle helmets are highly effective at preventing head injury during head impact: Head-form accelerations and injury criteria for helmeted and unhelmeted impacts. In: Accident Analysis & Prevention, vol. 70, p. 1-7.

Rådet for Sikker Trafik / Epinion Copenhagen (2016), Cyklistundersøgelse [survey on cyclists], Copenhagen.

Elvik, R. (2013). Corrigendum to: “Publication bias and time-trend bias in meta-analysis of bicycle

helmet efficacy: A re-analysis of Attewell, Glase and McFadden, 2001” [Accid. Anal. Prev. 43 (2011) 1245–1251]. In: Accident Analysis & Prevention, vol. 60, p. 245–253.

Fahlstedt, M., Halldin, P. & Kleiven, S. (2016). The protective effect of a helmet in three bicycle accidents – A finite element study. In: Accident Analysis & Prevention, vol. 91, p. 135-143.

Fyhri, A., Bjørnskau, T. & Backer-Grøndahl, A. (2012). Bicycle helmets – A case of risk compensation? In: Transportation Research Part F, vol. 15, p. 612-624.

Folksam (2015). Bicycle helmet test 2015. Folksam, Stockholm, Sweden.

Goldenbeld, C., Vugt, M.J.H. van & Schaalma, H. (2003). De fietshelm wint terrein in Nederland. In: Tijdschrift voor Gezondheidswetenschappen, vol. 81, nr. 1, p. 18-23.

Goldenbeld, C., Boele, M.J. & Commandeur, J.J.F. (2016). Evaluatie fietshelmcampagne 'Coole kop, helm op!' in Zeeland; Effecten op helmgebruik en factoren van invloed. R-2016-8. SWOV, Den Haag.

Hagel, B., Macpherson, A., Rivara, F.P. & Pless, B. (2006). Arguments against helmet legislation are flawed. In: British Medical Journal, vol. 332, nr. 7543, p. 725-726.

Hövding (2016). Hövding airbag for urban cyclists. http://www.hovding.com/, bekeken op 18 augustus 2016.

Jong, P. de (2012). The health impact of mandatory bicycle helmet laws. In: Risk Analysis, vol. 32, nr. 5, p. 782-790.

Kemler, H.J., Ormel, W., Jonkhoff, L., Klein Wolt, K., et al. (2009). De fietshelm bij kinderen en jongeren; onderzoek naar de voor- en nadelen. Stichting Consument en Veiligheid, Amsterdam.

Kraemer, J.D. (2016). Helmet laws, helmet use, and bicycle ridership. In: Journal of Adolescent Health, vol. 59, nr. 3, p. 338-344.

Lajunen, T. (2015). Barriers and facilitators of bicycle helmet use among children and their parents. In: Transportation Research Part F, vol. 41, p. 294-301.

Mizuno, K., Ito, D., Yoshida, R., Masuda, H., et al. (2014). Adult headform impact tests of three Japanese child bicycle helmets into a vehicle. In: Accident Analysis & Prevention, vol. 73, p. 359-372.

Newbold, S.C. (2012). Examining the health-risk tradeoffs of mandatory bicycle helmet laws. In: Risk Analysis, vol. 32, nr. 5, p. 791-798.

Olivier, J., Boufous,S. & Grzebieta, R. (2016). No strong evidence bicycle helmet legislation deters cycling. In: Medical Journal Australia, vol. 205, nr. 2, p. 54-55.

Olivier, J. & Creighton, P. (2016). Bicycle injuries and helmet use: a systematic review and meta-analysis. In: International Journal of Epidemiology, p. 1-15.

Olivier, J., Wang, J.J.J., Walter, S. & Grzebieta, R. (2014). Anti-helmet arguments: lies, damned lies and flawed statistics. In: Journal of the Australasian College of Road Safety, vol. 25, nr. 4, p. 10-23.

Phillips, R.O., Fyhri, A. & Sagberg, F. (2011). Risk compensation and bicycle helmets. In: Risk Analysis, vol. 31, nr. 8, p. 1187-1195.

Pierce, S.R., Palombaro, K.M. & Black, J.D. (2014). Barriers to bicycle helmet use in young children in an urban elementary school. In: Health Promotion Practice, vol. 15, nr. 3, 406-412.

Richard, J.-B., Thélot, B. & Beck, F. (2013). Evolution of bicycle helmet use and its determinants in France: 2000–2010. In: Accident Analysis and Prevention, vol. 60, p. 113-120.

Robinson, D.L. (2006). Do enforced bicycle helmet laws improve public health? No clear evidence from countries that have enforced the wearing of helmets. In: British Medical Journal, vol. 332, nr. 7543, p. 722-725.

Ross, T.P., Ross, L.T., Rahman, A. & Cataldo, S. (2010). The bicycle helmet attitudes scale: Using the health belief model to predict helmet use among undergraduates. In: Journal of American College Health, vol. 59, nr. 1, p. 29–36.

Schepers, J.P., Jager, K. de & Hulshof, R. (2016). Speed-pedelec wordt bromfiets: wat verandert er en wat zijn de gevolgen. Notitie, versie 1. Fietsberaad, Utrecht.

Sieg, G. (2014). Costs and benefits of a bicycle helmet law for Germany. Institute of Transport Economics Münster. Working Paper No. 21, Münster.

Towner, E., Dowswell, T., Burkes, M., Dickinson, H., et al. (2002). Bicycle helmets - a review of their effectiveness; A critical review of the literature. Road Safety Research Report 30. Department for Transport DfT, London.

Walker, I. (2007). Drivers overtaking bicyclists: Objective data on the effects of riding position, helmet use, vehicle type and apparent gender. In: Accident Analysis and Prevention, vol. 39, nr. 2, p. 417 425.

Weijermars, W.A.M., Stipdonk, H.L., Aarts, L.T., Bos, N.M., et al. (2014). Verkeersveiligheidsbalans 2000-2012; Oorzaken en gevolgen van verkeersonveiligheid. R-2014-24. SWOV, Den Haag.

Wijlhuizen, G.J. & Gent, P. van (2014). Race- en toerfietsen: mogelijkheden voor meer veiligheid; Vragenlijststudie en expertbeoordeling. R-2014-24A. SWOV, Den Haag.

Zeegers, T. (2015). Fabels over de fietshelm. Bijdrage Nationaal Verkeerskundecongres, 5 november 2015, Zwolle.

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Updated

01 Oct 2016