Scientific Journal Articles
on Bike Safety and Helmets
Summary: Here are references to a few of the many medical and scientific journal articles on the Web about helmets and bicycle safety. Most sources provide only the abstract summary for free. The articles below are in sections:
Systematic Review of Childhood Injury Prevention Interventions available on the Harborview Web page. Summarizes the problem and evaluates intervention methods. Harborview also has a page up summarizing the results of a number of studies of helmet effectiveness. Highly recommended, although the studies cited are a decade or more old.
The Big One: The New England Journal of Medicine article describing the Thompson and Rivara studies documenting the effectiveness of bicycle helmets. There are references at the bottom to other medical journal articles. This article is the authoritative source most often quoted on the potential for injury reduction by wearing a helmet.
Effectiveness of bicycle safety helmets in preventing head injuries. A case-control study is a second study from the same team. The Journal of the American Medical Association changes URL's from time to time. If the links do not work, this search for helmet articles on the JAMA site should find most of them.
And a more recent study from Australia: The effectiveness of helmets in bicycle collisions with motor vehicles: A case–control study. This 2013 study showed that "Helmet use was associated with reduced risk of head injury in bicycle collisions with motor vehicles of up to 74%, and the more severe the injury considered, the greater the reduction. This was also found to be true for particular head injuries such as skull fractures, intracranial injury and open head wounds. Around one half of children and adolescents less than 19 years were not wearing a helmet, an issue that needs to be addressed in light of the demonstrated effectiveness of helmets. Non-helmeted cyclists were more likely to display risky riding behaviour, however, were less likely to cycle in risky areas; the net result of which was that they were more likely to be involved in more severe crashes."
A computational simulation study of the influence of helmet wearing on head injury risk in adult cyclists
Simulations were run over a range of bike and car speeds. Bicycle helmets were found to be effective in reducing the severity of head injuries sustained in frequent crashes. They reduced the risk of a severe (greater than AIS3) injury in crashes with head impacts by an average of 40%. In crashes likely to cause up to moderate (AIS2) injuries to an unprotected rider, a helmet eliminated the risk of injury. Helmets were also found to prevent fatal head injuries in some instances. The study demonstrated the effectiveness of helmets over the entire range of speeds. Helmets were also found to be protective of neck injuries in many cases. Helmets offered an increase in protection even when an increase in speed due to risk compensation was factored in. There are illustrations of the simulations on the linked web site.
Bicycle-associated head injuries and deaths in the United States from 1984 through 1988. How many are preventable?
Circumstances and Severity of Bicycle Injuries - Summary Report of Harborview Helmet Studies A study sponsored by the Snell Foundation and published by Snell, not a journal. Has interesting data on the location of helmet impacts.
Use of Alcohol as a Risk Factor for Bicycling Injury From the Journal of the American Medical Association.
Elevated Blood Alcohol and Risk of Injury Among Bicyclists From the Journal of the American Medical Association.
Caloric Imbalance and Public Health Policy. This 1999 article from the Journal of the American Medical Association discussed obesity and exercise, a prime reason for promoting bicycle use, opening with a statement that obesity had become an epidemic.
Alcohol and Motor Vehicle-Related Deaths of Children as Passengers, Pedestrians, and Bicyclists From the Journal of the American Medical Association.
Unpowered Scooter-Related Injuries--United States, 1998-2000. (You have to page forward in this .pdf file to find the article.) From the Journal of the American Medical Association.
Helmet legislation effectiveness in three NY counties - Dr Douglas R. Puder et. al. of the Department of Pediatrics, Nyack Hospital, Nyack NY
November, 1999, issue of the American Journal of Public Health.
Risk Factors for Injuries from in-Line Skating and the Effectiveness of Safety Gear
Bicycle helmet use by children. Evaluation of a community-wide helmet campaign. From the Journal of the American Medical Association.
Profile of Pediatric Bicycle Injuries from the Southern Medical Journal. "Bicycle injuries accounted for 18% of all pediatric trauma alert patients. The mean age of injured children was 10 years, and 79% were males. Bicycle-motor vehicle collisions caused 84% of injuries. Only 3 children (1.4%) wore bicycle helmets. Resulting injuries included external wounds (86%), head injuries (47%), fractures (29%), and internal organs (9%). Six children died. You have to register with Medscape to read the article, but it's free.
The Cost of Traumatic Brain Injury
and Its Prevention in the United States by Ted R. Miller, Eduard Zaloshnja, and Delia Hendrie is a chapter in the book Neurotrauma and Critical Care of the Brain by U. Drews and Christopher M. Loftus. Midway through the chapter (p 453) it presents a return on investment analysis of the value of bicycle helmets. The book was published in 2009, so the numbers are still reasonably current.
Influence of Socioeconomic Status on the Effectiveness of Bicycle Helmet Legislation for Children: A Prospective Observational Study
Patricia C. Parkin, MD, Amina Khambalia, MSc, Leanne Kmet, MSc, Colin Macarthur, MBChB, PhD.
PEDIATRICS Vol. 112 No. 3 September 2003, pp. e192-e196 ELECTRONIC ARTICLE
Abstract says "This study showed that bicycle helmet use by children increased significantly after helmet legislation. In this urban area with socioeconomic diversity and in the context of prelegislation promotion and educational activities, the legislative effect was most powerful among children who resided in low-income areas."
Bicycle Helmet Use Among Maryland Children: Effect of Legislation and Education. Timothy R. Coté, Jeffrey J. Sacks, Marcie-jo Kresnow, Deborah A. Lambert-Huber, Ellen R. Schmidt, Andrew L. Dannenberg, and Cynthia M. Lipsitz Pediatrics, Jun 1992; 89: 1216 - 1220. Prelaw and postlaw helmet use was observed in Howard County (with a pre-law police campaign) and two control counties: Montgomery (with a community education program) and Baltimore County (no helmet activities). Prelaw helmet use rates for children were 4% for Howard, 8% for Montgomery, and 19% for Baltimore. Postlaw rates were 47%, 19%, and 4%, respectively.
Children's bicycle helmet use and injuries in Hillsborough County, Florida before and after helmet legislation
K D Liller et al. Explored the changes in children's bicycle helmet use and motor vehicle bicycle related injuries in Hillsborough County, Florida before and after passage of the state bicycle helmet law. The results show a significant increase in bicycle helmet use among children, ages 5–13, in the post-law years compared with the pre-law years. Also, there has been a significant decline in the rates of bicycle related motor vehicle injuries among children in the post-law years compared with the pre-law years. Although there have been complementary educational and outreach activities in the county to support helmet use, it appears that the greatest increase in use occurred after the passage of the helmet law.
An Outstanding Science Fair Project: J. Raleigh Burt produced a 2005 science project called Dangerous Decision: The Consideration for Helmet Use At Any Speed". He convincingly demonstrates that a simple tipover fall from a bicycle onto pavement at zero forward speed can cause a head injury, and further concludes that helmets meeting current standards are likely to prevent it. The project won awards at two Colorado state-level science fairs. You can read about it and download a full copy of the paper.
Children Should Wear Helmets While Ice-Skating: A Comparison of Skating-Related Injuries. An article comparing head injuries in skateboarding, roller skating, inline skating and ice skating that appeared in the July, 2004 edition of Pediatrics. The authors found similar head injury patterns and recommended that ice skaters wear helmets.
Preventing bicycle-related injuries: next steps Frederick Rivara and Richard W Sattin. Injury Prevention 2011;17:215 doi:10.1136/injuryprev-2011-040046. Bicycling can be a valuable part of the program to deal with obesity. Head injury is a discouragement to riding. "Head injury is by far the greatest risk posed to bicyclists, comprising one-third of emergency department visits, two-thirds of hospital admissions, and three-quarters of deaths. "Since 1999, in the USA, the number and rate of bicycle-related deaths has decreased for those aged 16 years or less from 213 (0.31 per 100?000) to 118 (0.17 per 100?000) in 2007.2 The number and rate of cycle-related deaths for those aged 17 or more, however, has increased during that same period from 586 (0.28 per 100?000) to 700 (0.30 per 100?000). Among those aged 16 or less, the number of non-fatal bicycle-related injuries in the USA decreased from about 316,000 in 2001 to 261,000 in 2009, whereas for those older than 16, the number of injuries increased from about 202,000 in 2001 to 258,000 in 2009." The authors cite Insurance Institute for Highway Safety stats. They
discuss strategies to promote cycling, off-road trails, factors that might alter the risk of injury to road cyclists, mountain biking injuries and low rates of helmet use nationwide. They conclude that "New research, different approaches, and better implementation of findings" are needed.
Bicycle-Related Injuries Among Children and Adolescents in the United States.
Mehan TJ, Gardner R, Smith GA, McKenzie LB. Clin Pediatr 2008; ePub(ePub): ePub.
Describes the epidemiology of US bicycle-related injuries among children and adolescents 18 years and younger. Analyzes NEISS data for patients seen in emergency rooms 1990 to 2005 who were injured while operating a bicycle. During the study period an estimated 6,228,700 individuals 18 years and younger were treated for bicycle-related injuries. Children with head injuries were more than 3 (relative risk, 3.63) times as likely to require hospitalization and were almost 6 (relative risk, 5.77) times more likely to have their injuries result in death. The authors concluded that the large number of bicycle-related injuries indicates that prevention of these injuries should remain an important area of bicycle safety research and practice.
Bicycle Helmet Assessment During Well Visits Reveals Severe Shortcomings in Condition and Fit Gregory W. Parkinson, MD, FAAP and Kelly E. Hike, BA, Falmouth Pediatric Associates, Falmouth, MA. PEDIATRICS Vol. 112 No. 2 August 2003, pp. 320-323. Results. Eighty-four percent (395/473) of eligible families participated. A total of 479 participants were assessed. Eighty-eight percent of participants (419/478) owned a helmet. Reported helmet use "always" or "almost always" was 73% for bicycling (317/434), 69% for in-line skating (193/279), 58% for scootering (179/310), and 50% for skateboarding (79/158). Compared with younger children, teenagers were less likely to wear helmets for all activities. Complete pass rate for every aspect of condition and fit was 4% (20/478, 95% confidence interval: 3–6). The pass rate when the parent alone fit the helmet was 0% (0/52). Three individual aspects of fit were most problematic: 1) helmet ‘resting position’ too high on the forehead (pass rate 249/479; 52%), 2) improper strap position (pass rate 157/476; 33%), and 3) excessive movement of the helmet from front to back of the head (pass rate 247/479; 52%). Mean time for questionnaire completion was 4 (standard deviation: ±1) minutes, and 7 (standard deviation: ±3) minutes for helmet assessment. Conclusions. Ninety-six percent of children and adolescents wore helmets in inadequate condition and/or with inadequate fit. This occurred despite a high acceptance of helmet use by this population.
Lights Out: Can contact sports lower your intelligence? This article appeared in Discover Magazine. Although not a peer-reviewed journal article, it is available to the public for free, and is a very interesting source of info on concussion levels and mechanisms.
Bicycle safety helmet legislation and bicycle-related non-fatal injuries in California by Brian Ho-Yin Lee, Joseph L. Schofer and Frank S. Koppelman. Accident Analysis & Prevention, Volume 37, Issue 1 , January 2005, Pages 93-102. Compared developments in injury rates in California after adoption of helmet legislation covering kids. Adult rates did not change, while traumatic brain injuries among child riders went down 18%. We have a lot of questions about the data and the assumptions of this study. Available online for $30.
Research sponsored by the NFL Players Association developed a lot of good info on concussion. Here is another Neurosurgery article from that data concluding that "dementia-related syndromes may be initiated by repetitive cerebral concussions in professional football players."
This Cochrane Collaboration study found that helmet legislation "appears to be effective in increasing helmet use and decreasing head injury rates in the populations for which it is implemented. However, there are very few high quality evaluative studies that measure these outcomes, and none that reported data on possible declines in bicycle use."
Intended and Unintended Effects of Youth Bicycle Helmet Laws a paper on the University of California - Irvine Department of Education site that concludes that passing a state-wide bicycle helmet law reduces cycling by those who are covered by the law by 4 to 5 per cent.
Demographic, socioeconomic, and attitudinal associations with children's cycle-helmet use in the absence of legislation and article that concludes using self-reported data from school kids that attitudes are probably the most important determinant of helmet wearing. We have not seen the whole article and can't imagine how the result could have been different. But we never put any stock in child studies using self-reported data anyway, since the kids tell you whatever they think they should be telling you.
Motorcycle helmets do not injure necks reports this 2011 page on a Johns Hopkins study. We don't have the journal citation for it.
Awareness of the bicycle helmet law in North Carolina reports on a study using a written survey that found that the majority of those returning the survey said they were aware that North Carolina has a helmet law.
The effectiveness of helmets in bicycle collisions with motor vehicles: A case–control study. This 2013 study showed that "Helmet use was associated with reduced risk of head injury in bicycle collisions with motor vehicles of up to 74%, and the more severe the injury considered, the greater the reduction. This was also found to be true for particular head injuries such as skull fractures, intracranial injury and open head wounds. Around one half of children and adolescents less than 19 years were not wearing a helmet, an issue that needs to be addressed in light of the demonstrated effectiveness of helmets. Non-helmeted cyclists were more likely to display risky riding behaviour, however, were less likely to cycle in risky areas; the net result of which was that they were more likely to be involved in more severe crashes."
Long term bicycle related head injury trends for New South Wales, Australia following mandatory helmet legislation. This long term study of the effects of the mandatory helmet law in New South Wales found indicators that cycling has increased and head injuries have dropped over time. "Highlights: Decline in bicycle related head injuries attributable to mandatory helmet legislation (MHL) has been maintained over the following two decades. The adjusted estimated post-MHL decline in bicycle related injuries is larger than the immediate impact previously reported (from 29% to 50%). Increase in cycling numbers post-MHL is associated with a similar increase in injuries with the exception of head injuries. A recent decline in cycling injuries and a continued increase in cycling numbers is associated with expenditures on cycling infrastructure. The decline in injuries attributable to cycling infrastructure is more pronounced for head injuries. Here is a summary by the authors. Posting comments on this blog the critics continue to debate.
Bicycle Injury Hospitalisations and Deaths in Western Australia - 1981-1995. An Australian Government publication showing that "There was a decrease in the proportion of head injuries from almost half in 1981-1983 to just over a third in 1993-1995..." Now only available from the National Library of Australia.
CR 195: Bicycle helmets and Injury Prevention: A Formal Review (2000)
"Bicycle helmet efficacy is quantified using a formal meta-analytic approach based on peer-reviewed studies...The results are based on studies conducted in Australia, the USA, Canada and the United Kingdom, published in the epidemiological and public health literature in the period 1987- 1998. The summary odds ratio estimate for efficacy is 0.40 (95% confidence interval 0.29, 0.55) for head injury, 0.42 (0.26, 0.67) for brain injury, 0.53 (0.39, 0.73) for facial injury and 0.27 (0.10, 0.71) for fatal injury. This indicates a statistically significant protective effect of helmets." BHSI note: Most of the "helmets" in pre-1987 days were not capable of meeting today's standards. If the study were redone with more recent data we would expect a more protective effect would emerge.
Monograph 5 - Bicycle Helmet Research Centre for Accident Research & Road Safety - Queensland (CARRS-Q), November 2010. This is a thorough study of bicycle helmet effectiveness and issues, recommending that helmet laws in Queensland should not be changed. The conclusion in part says:
"Current bicycle helmet wearing rates are halving the number of head injuries experienced by Queensland cyclists. This is consistent with published evidence that mandatory bicycle helmet wearing legislation has prevented injuries and deaths from head injuries.
It is reasonably clear that it discouraged people from cycling twenty years ago when it was first introduced. Having been in place for that length of time in Queensland and throughout most of Australia, there is little evidence that it continues to discourage cycling. There is little evidence that there is a large body of people who would take up cycling if the legislation was changed."
The Cochrane Collaboration and Bicycle Helmets. This one is a rant from the May, 2005 issue of Accident Analysis & Prevention about the Thompson, Rivara and Thompson study that leads off this list. The author, Aussie W. J. Curnow, feels that the data is stale and that helmets have changed. He says hard shell helmets are "rare" (they must not have skate-style, downhill racing or BMX helmets in Australia) and that the protection of soft shells has not been proven. He has lots of other complaints too, none of which we consider valid. On top of that, it cost us $30 to read it. But you can read the abstract for free.
And here is the rebuttal, for another $30, from two authors in Canada.
These articles illustrate the problem with publishing your material in a journal--the information is buried behind expensive walls.
Formal retraction of a paper by Voukelatos and Rissel by the Journal of the Australasian College of Road Safety. It cites persistent "data errors" as the cause. The paper had concluded that helmet laws did not result in fewer head injuries.
Impact of mandatory helmet legislation on bicycle-related head injuries in children: a population-based study.
Macpherson AK, To TM, Macarthur C, Chipman ML, Wright JG, Parkin PC.
Pediatrics 2002; 110(5):e60. Examines the effect of helmet laws on the rate of head injuries in four Canadian provinces. The bicycle-related head injury rate declined significantly (45% reduction) in provinces where legislation had been adopted compared with provinces and territories that did not adopt legislation (27% reduction). (Copyright © 2002 American Academy of Pediatrics--full article is free on the Web.)
Bicycle Helmet Use in British Columbia: Effects of the Helmet Use Law reports on an evaluation conducted at the University of North Carolina of the effectiveness of the BC law.
Trends in pediatric and adult bicycling deaths before and after passage of a bicycle helmet law. An article about Ontario death rates after a helmet law was passed. Appeared in PEDIATRICS Vol. 122 No. 3 September 2008, pp. 605-610 (doi:10.1542/peds.2007-1776) The article examines bicycle-related mortality rates in Ontario, Canada, before and after helmet legislation. "For bicyclists 1 to 15 years of age, the average number of deaths per year decreased 52%, the mortality rate per 100000 person-years decreased 55%, and the time series analysis demonstrated a significant reduction in deaths after legislation." But for bicyclists 16 and over, there was no significant change. "These findings support promotion of helmet use, enforcement of the existing law, and extension of the law to adult bicyclists."
The effects of provincial bicycle helmet legislation on helmet use and bicycle ridership in Canada by Jessica Dennis, Beth Potter, Tim Ramsay and Ryan Zarychanski. Journal of Injury Prevention, August 2010.
Data shows that bicycle usage remained constant after helmet laws were adopted in two provinces, and that helmet use was increased more by all-ages laws than by laws applying only to children. Helmet use data came from surveys, not actual observation.
Trends in Pediatric and Adult Bicycling Deaths Before and After Passage of a Bicycle Helmet Law. David E. Wesson, Derek Stephens, Kelvin Lam, Daria Parsons, Laura Spence, and Patricia C. Parkin. Pediatrics, Sep 2008; 122: 605 - 610. Examines bicycle-related mortality rates in Ontario, Canada, from 1991 to 2002 among bicyclists 1 to 15 years of age and 16 years of age through adulthood and to determine the effect of legislation (introduced in October 1995 for bicyclists less than 18 years of age) on mortality rates. The authors found that "For bicyclists 1 to 15 years of age, the average number of deaths per year decreased 52%..." Concludes that "The bicycle-related mortality rate in children 1 to 15 years of age has decreased significantly, which may be attributable in part to helmet legislation. A similar reduction for bicyclists 16 years of age through adulthood was not identified. These findings support promotion of helmet use, enforcement of the existing law, and extension of the law to adult bicyclists." Full article is free on the Web.
Bicycle helmet use after the introduction of all ages helmet legislation in an urban community in Alberta, Canada. Karkhaneh et al. Canadian Journal of Public Health, Vol 102, No 2, April 25, 2011. Evaluated the effect of mandatory bicycle helmet legislation for all ages in St. Albert, Alberta, using actual field observations. Helmet use increased from 45% to 92% (PR = 2.03; 95% CI: 1.72-2.39) post-legislation. Controlling for other covariates, children were 53% (PR = 1.53; 95% CI: 1.34-1.74) and adolescents greater than 6 times (PR =6.57; 95% CI: 1.39-31.0) more likely to wear helmets; however, adults (PR = 1.26; 95% CI: 0.96-1.66) did not show a statistically significant change post-legislation. CONCLUSIONS: Helmet legislation in St. Albert was associated with a significant increase in helmet use among child and adolescent cyclists. Here is an article about the study from the Global Winnipeg online news service.
The impact of compulsory cycle helmet legislation on cyclist head injuries in New South Wales, Australia Scott R. Walter, Jake Olivier, Tim Churches, Raphael Grzebieta. Accident Analysis & Prevention, July, 2011. Hospital data modeled the ratio of head to limb injuries and found that cyclist head injuries decreased more than limb injuries at time of legislation. This article reports contrary views, but the paper they were based on has been retracted by the publisher for errors. Jake Olivier wrote a further article about this situation.
Peer and Adult Companion Helmet Use Is Associated With Bicycle Helmet Use by Children. Amina Khambalia, Colin MacArthur, and Patricia C. Parkin. Pediatrics, Oct 2005; 116: 939 - 942. A Toronto study that concluded that helmet use by children is closely correlated with use of helmets by their peers and parents. Free on the Web.
Head first: Bicycle-helmet use and our children’s safety This Canadian article reviews Canadian injury and helmet use stats, as well as the effect of mandatory helmet laws. The authors conclude that legislation is called for in the remaining provinces who do not have laws.
A Review of All Accidental Cycling Deaths in Ontario From January 1st, 2006 to December 31st, 2010 This study by the Ontario Coroner found that "Only 27% (35 of 129) of those who died as the result of a cycling collision were wearing a helmet. Despite mandatory legislation, only 44% (7 of 16) of cyclists under the age of 18 who died were wearing a helmet. Those cyclists whose cause of death included a head injury were three times less likely to be wearing a helmet than those who died of other types of injuries." They recommended many measures including a complete streets approach to facilities, safety education, legislative changes, paved shoulders, more enforcement, side guards on heavy trucks and a mandatory helmet law for all ages as part of a helmet promotion campaign.
Liberty or Death; Don't Tread on Me Another British paper decrying the ethics of taking liberties away by requiring helmets on adults. (Not so bad for kids.)
The core contention: "The right not to wear helmets is part of a more general right to determine how much risk to take with our health . . .we all have a strong interest in having the freedom to take risks with our own health and this general right should, prima facia, be protected however it is expressed." We consider that a legitimate point of view, but the authors go on to attack the effectiveness of helmets in an attempt to bolster their ethics argument. "First, cycle helmets in their present form may not be capable of providing significant levels of protection to the skull and brain." There are many other references on this page refuting that, and refuting their contention that cycling is so intrinsically safe that nobody needs a helmet. The paper is intended to counter the British Medical Association's 2010 recommendation to pass a universal UK helmet law. But there is nothing new here. There are many references to tired old publications from the 20th century, although the ages of some are obfuscated by "accessed on the Web" dates. Curiously, the authors say they don't really believe in the American sentiments they chose for the title.
Legislation for the compulsory wearing of cycle helmets a report of the British Medical Association's Board of Science and Education. November 2004. The BMA examined the evidence and recommended in 2004 that the UK adopt a mandatory helmet law for both children and adults. They had previously recognized the benefits of helmet use but had feared that a helmet law might reduce cycling.
The Potential for Cycle Helmets to Prevent Injury: a Review of the Evidence a report by the UK's Transport Research Laboratory
attempting to estimate the effectiveness of helmets. The authors, D. Hynd and R. Cuerdon, found that in 2008, 34 per cent of riders in the UK were wearing helmets on major roads, and 17 per cent on minor roads. There are findings on helmet effectiveness, with the estimate of lives saved by helmets reduced because many of the London cases examined were cyclists crushed by trucks and busses.
Inequalities in cycle helmet use: cross sectional survey in schools in deprived areas of Nottingham. This UK study showed that helmet use in low income areas increased in response to a free helmet program.
Alcohol Intake and the Pattern of Trauma in Young Adults and Working Aged People Admitted After Trauma. This 2004 study in Finland demonstrates a link between alcohol and bicycle crashes in that country.
Bicycle helmet wearing and the risk of head, face, and neck injury: a French case-control study based on a road trauma registry
Amoros, Chiron, Martin, Laumon. Injury Prevention, doi:10.1136/ip.2011.031815. Results: The fully adjusted ORs of helmeted versus unhelmeted cyclists are: for AIS1+ head injuries, 0.69 (95% CI 0.59 to 0.81); for AIS3+ head injuries sustained in urban areas, 0.34 (95% CI 0.15 to 0.65), those sustained in rural areas, 0.07 (95% CI 0.02 to 0.23); for AIS1+ facial injuries, 0.72 (95% CI 0.62 to 0.83); and for AIS1+ neck injuries, 1.18 (95% CI 0.94 to 1.47).
Conclusion: This study confirms the protective effect for head and facial injuries, even though soft-shell helmets have now become more common. The reduction of risk is greater for serious head injuries. The study is inconclusive about the risk for neck injuries.
Risk Compensation: A Male Phenomenon? Results From a Controlled
Intervention Trial Promoting Helmet Use Among Cyclists. The authors of this French study measured the speed of adult urban bicycle riders who had new helmets, and others who did not. The riders were enrolled in a controlled intervention trial. If helmeted riders rode faster, in theory it would indicate that they were feeling safer because of the helmet and were riding faster to achieve the same level of risk they normally experienced without a helmet. The authors state that "In conclusion, helmet use did not result in increased risk-taking among female cyclists. The average speed difference between helmeted and nonhelmeted male cyclists was moderate and tended toward zero as overall speed increased." Although the statistical techniques are sophisticated, the data was sparse (only 3.8% of the observations were helmeted riders) and there are many potentially confounding factors not explained. Risk-taking on a bicycle is not just a matter of speed. The download costs $20, but here is a much more detailed article on the same study with free access:
Investigating Helmet Promotion for Cyclists: Results from a Randomised Study with Observation of Behaviour, Using a Semi-Automatic Video System. This article gives a much better appreciation of this extraordinary study.
Incidence and risk factors of severe traumatic brain injury resulting from road accidents: A population-based study. This French study found that the head injury fatality rate increased from 20% in childhood to 71% over 75-year-old. Compared to restrained car occupants, the odds ratio for having a severe head injury was 18.1 for un-helmeted motorcyclists, 9.2 for pedestrians, 6.4 for un-helmeted cyclists, 3.9 for unrestrained car occupants and 2.8 for helmeted motorcyclists. Even after adjustment for several severity factors, male gender and age above 55 were both risk factors. The authors advocated prevention programs to improve head protection. $30 for the download.
This abstract of a German meeting paper is titled Specific patterns of bicycle accident injuries - An analysis of correlation between level of head trauma and trauma mechanism. Although not a journal article, it was presented in 2004 to a Joint Meeting of the Ungarischen Gesellschaft für Neurochirurgie and the Deutsche Gesellschaft für Neurochirurgie. The authors noted that cyclists with and without helmets had about the same head injuries, and concluded that helmets were not working. Although it is difficult to tell from just the abstract, their conclusion seemed to miss the point. For helmeted riders to be included in their data the cyclist had to be head-injured despite wearing a helmet. But there is no indication of any effort to determine how many cyclists had not been included in their study because the helmet prevented their injury, and there is no indication that they knew how hard a blow the helmeted and unhelmeted riders had suffered. So bare-headed riders injured in lesser impacts were compared with helmeted riders probably injured in much harder impacts after the helmet's protection had been used up, impacts where a bare-headed rider would have perhaps died and not been included in a clinical study. We count this one in the ranks of papers written to prove a point that the authors had already decided on.
Evaluation of New Zealand’s bicycle helmet law
Colin F Clarke. New Zealand Medical Journal 10 February 2012, Vol 125 No 1349; ISSN 1175 8716. Concludes that New Zealand's helmet law "has failed in aspects of promoting cycling, safety, health, accident compensation, environmental issues and civil liberties." This British author details a decline in cycling in New Zealand, but with no evidence that the helmet law caused it. The full article is available on the cycle-helmets.com site.
The rationale for promotion of bicycle helmet legislation for children up to 18 years (Israel) an article reviewing the evidence showing the effectiveness of helmets and setting out reasons why Israel should adopt legislation requiring them.
Bicycle helmets, risk compensation and cyclist types This Norwegian study indicates that there are complex issues in determining how much risk compensation cyclists might do when they use helmets. The conclusion: "The use of [a] bicycle helmet as such does not seem to be related to either accident proneness or speeding."
A Study of the Effectiveness of Bicycle Safety Helmets Among Children in Skaraborg County, Sweden
(1991) Ekman, R and Welander, G. - Karolinska Institute, Department of Social Medicine, Kronan Health Center and Skaraborg County Council, Department of Health Promotion, Sit Olafsgatan 46, S-52135 Fallioping, Sweden
A decrease in both mild and severe bicycle-related head injuries in helmet wearing ages - trend analyses in Sweden Peter Berg and Ragnar Westerling, Oxford Journals-Medicine-Health Promotion International, Vol. 22, Issue 3, pp.191-197. Analyzes trends of bicycle-related head injuries in Sweden by different age groups. Many references, good discussion of data difficulties regarding exposure levels and helmet use.
Characteristics of bicycle-related head injuries among school-aged children in Taipei area. Wang et al, Department of Emergency Medicine, Taipei Medical University Hospital, Taipei 110, Taiwan. A study of head injuries suffered by child bicyclists in Taipei's incredible traffic. Concludes that "For children whose main mode of transport is bicycles, the enforcement of helmet legislation, educational programs in bicycling safety and equipment, and improving the infrastructure for bicycling in urban areas are needed in Taiwan to reduce potentially debilitating or life-threatening injuries." There is also a statistic about reduced head injuries to children whose bikes have reflectors that is cited by some helmet sceptics as invalid.
Skid Tests on a Select Group of Bicycle Helmets
to Determine Their Head-Neck Protective Characteristics by Voigt Hodgson of Wayne State University. A study published by the Michigan Department of Public Health in 1991. Hard shell, micro shell and no-shell helmets were impacted into slanted concrete. Helmets with shells slid better, resulting in lower linear g's to the headform (your brain). "Test results predict that hard and micro-shell helmets provide about equal protection from cervical spine injury. The hard and micro-shell helmets tended to slide rather than hang up on impact with concrete. This sliding tendency was the mechanism that reduced the potential for neck injury." This is part of the scientific justification for our Rounder, Smoother, Safer slogan.
Chin strap forces in bicycle helmets. A study by Torbjorn Andersson of the Swedish National Testing & Research Institute. Published in the International Journal of Injury Control and Safety Promotion, Vol. 2, Issue 1 March 1995, pp 1-11. DOI: 10.1080/09298349508945743. Measured forces on bike helmet chin straps during impacts on asphalt. Tested with hard shell, no shell and a ribbed helmet with large vents. The test dummy was suspended from the ceiling impacted by a chunk of asphalt. Chin strap forces differed appreciably. "The shell helmets did not grip the asphalt layer at all and did not rotate, which implies that the headform did not rotate either. The non-shell helmets gripped the asphalt layer
in each impact, rotated and transferred this rotation to the headform." This is part of the scientific justification for our Rounder, Smoother, Safer slogan.
The influence of reduced friction on head injury metrics in helmeted head impacts. An article on what a slippery helmet means when you crash, going beyond earlier publications to assess the likelihood of injury using rotational forces as the criterion. Appeared in Traffic Injury Prevention, Volume 9, Issue 5 October 2008 , pages 483 - 488. DOI: 10.1080/15389580802272427.
The article explores the possibility that in some cases reducing surface friction of a helmet in a crash could increase head injury risk. The goal of was "to demonstrate that reducing friction on the surface of a helmet decreases the rotational acceleration of the head in some scenarios and increases it in other scenarios and to discuss the implications for helmet design." The authors conclude that "The theoretical considerations presented here could be interpreted
into a design criterion as follows: friction should be
reduced for each point on the helmet surface until the cone defined
by the friction angle and the surface normal at that point no
longer includes the center of gravity of the head-helmet system.
Reducing friction beyond this point is not costly in an averaged
sense but neither is it beneficial. It is worth emphasizing that
this study has shown that substantial improvements in helmet
performance can result from a reduction in the coefficient of
friction and these findings are supported by other studies (Aare
and Halldin, 2003). Furthermore, we argue that while friction may be beneficial in a particular impact, in an averaged sense it is never beneficial and may be quite costly." This article has implications for our rounder, smoother, safer theme, and supports our views.
Protective Effect of Different Types of Bicycle Helmets. A Norwegian study by Kari Schroder Hansen et al published in 2003 in Traffic Injury Prevention comparing injury rates in hard shell and "foam" helmets. The authors concluded that "The use of hard shell helmets reduced the risk of getting injuries to the head. Children less than nine years old that used foam helmets had an increased risk of getting face injuries. All bicyclists should be recommended to use hard shell bicycle helmets while cycling." We have not seen the study and don't understand the conclusions.
Bicycle helmets: head impact dynamics in helmeted and unhelmeted oblique impact tests published in Traffic Injury Prevention, 2013. To assess the factors, including helmet use, that contribute to head linear and angular acceleration in bicycle crash simulation tests. Results: Helmet use was the most significant factor in reducing the magnitude of all outcome variables. Demonstrates that helmets do not increase angular head acceleration.
An overview of the state of the art in motorcycle helmets published in Accident Analysis and Prevention in 2013. This Portugese study covers helmet development, standards and a lot more, purporting to explain basics. We have read only the abstract.
2006 Skull Study Proves Bike Helmets Work. Original study by Dr. Chris A. Sloffer, a neurosurgical resident at the University of Illinois College of Medicine, in Peoria, et al. This report of the study says they dropped water-filled child skulls in helmets and the skulls did not fracture. We are not sure what that proves about reducing brain injury.
2012 Skull Study Proves Bike Helmets Work. Researchers at the Illinois Neurological Institute and Bradley University tested helmet performance in impact and crush tests with cadaver skulls. They found that helmet use can reduce by up to 87% the acceleration experienced by the skull during an impact and can aid the skull in resisting forces up to 470 pounds in a crush accident. Reference: Mattei TA, Bond BJ, Goulart CR, Sloffer CA, Morris MJ, Lin JJ: Performance analysis of the protective effects of bicycle helmets during impact and crush tests in pediatric skull models. Journal of Neurosurgery: Pediatrics, published online, ahead of print, October 2, 2012; DOI: 10.3171/2012.8.PEDS12116
Biokinetics Study of Rotation Acceleration for PHMA
A study of rotational acceleration effects using actual lab tests with bicycle helmets. Prepared by Biokinetics and Associates of Ottawa for the Protective Headgear Manufacturers Association (now defunct). We are grateful for permission to post this one, arranged by Biokinetics founder and helmet historian Jim Newman.
Bicycle Helmet Design. A paper by Mills and Gilchrist that appeared in Proceedings of the Institution of Mechanical Engineers. The authors, from the University of Birmingham in the UK, used finite element analysis to analyze theoretical oblique impacts of helmeted heads, concluding that "thicker foam liners of lower compressive yield stress can protect the head against linear acceleration in 150 J impacts. The peak rotational acceleration of the head was shown to be only slightly affected by the friction coefficient on the road and, in general, to be insufficient to cause serious diffuse brain injuries." When conclusions reached by finite element analysis disagree with studies conducted in physical labs, as the second finding does, the usual cause is the inadequacy of brain models.
Rational Approach to Pedal Cyclist Head Protection (and other titles) Doctoral thesis by Bart Depreitere. Date also used for articles in various journals and magazines. Analyzed head injuries of 86 pedal cyclists. Performed 12 mathematical accident recontructions (DADS-software) to estimate impact severity. Second phase was an impact study with ten human cadavers, showing longer energy pulses did more brain damage. A series of 81 impact tests on human skulls showed that energy response varied and suggested that a helmet filtering out skull base vibration could reduce some injuries. The author hopes that with more knowledge of brain injury better bicycle helmets will be possible. "In a limited series of impact tests on helmeted cadavers, it was found that helmets do not unequivocally reduce the head’s rotational acceleration and even may lead to increased accelerations. Helmets did not perform well either with respect to filtering out the frequencies (skull natural frequencies < 1500 Hz) at which the skull base vibration was most pronounced. In a third series of performance tests it was assessed whether helmets could prevent contact between the impactor and the temporal area in lateral impacts on helmeted cadavers. The helmets that did not cover the temporal area failed to protect it against such contacts and in one of these tests a skull fracture was produced." More of this analysis is available from various journal sites locatable by Googling.
This Google Scholar search found 28,000 scholarly links to bicycle helmet materials.
This search in the Journal of Pediatrics turned up 295 articles with the keyword helmets.
Science Direct has many more helmet articles, mostly available at about $30 each. They include articles on motorcycle helmet design and materials, bicycle helmet usage and finite element testing, and a range of article about other types of helmets. This search brought up hundreds of articles, not all of them directly relevant.
The Pedestrian Information Center page on Education Resources and Research has references to more than 150 studies and Web pages with bike program and safety info. Here is a search for "helmets" on their site.
Compendium of NHTSA research is a study by the US National Highway Traffic Safety Administration cataloging all of NHTSA's bike and pedestrian research over the years from 1969 to 2007. It is useful for references.
The SafetyLit service has journal articles by topic, and can send you an email every week with newly published peer-reviewed journal articles. Each weekly update has one section on Pedestrians and Bicycles, and one on Protective Headgear.
Our page for researchers has more sources.
This page was last revised on: September 10, 2013.