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:
The First 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 was the authoritative source most often quoted on the potential for injury reduction by wearing a helmet. But its statistical findings of 85% effectiveness were modified by the Second Big One, below and others that appeared subsequently.
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.
Helmet use and bicycle-related trauma injury outcomes Scott et al Journal of Brain Injury. Published online: 12 Sep 2019. Uses statistics from the National Trauma Data Bank. "Results: Of the 76,032 bicyclists with head/neck injury, 22% worn helmets. The lowest was among Blacks, Hispanics, and over 17 years old. Wearing a helmet significantly reduces injury severity, HLOS, ICULOS, and mortality (i.e total and in-hospital). Males had a severe injury, longer HLOS, ICULOS, and higher mortality than female. Blacks and Hispanics had longer HLOS and ICULOS and higher total mortality than Whites, but had a similar chance for in-hospital mortality."
A 2019 study Injuries associated with electric-powered bikes and scooters: analysis of US consumer product data published in Injury Prevention by DiMaggio et al.
found that E-bike and powered scooter injury patterns differ from more traditional pedal bicycles. Riders using E-bikes were more likely to suffer internal injuries and require hospital admission. Powered scooter injuries were nearly three times more likely to result in a diagnosis of concussion. E-bike-related injuries were also more than three times more likely to involve a collision with a pedestrian than either pedal bicycles or powered scooters, but found no evidence that powered scooters were more likely than bicycles to be involved in a collision with a pedestrian. While rates of pedal bicycle-related injuries have been decreasing, reported E-bike injuries have been increasing.
A 2017 study from
Traffic Injury Prevention is titled "Bicycle helmet effectiveness is not overstated." Conclusions: "Despite potential weaknesses with case-control study designs, the best available evidence suggests that helmet use is an effective measure of reducing cycling head injury."
A 2017 study from
International Journal of Epidemiology is titled "Bicycle injuries and helmet use: a systematic review and meta-analysis" Conclusions: "Bicycle helmet use was associated with reduced odds of head injury, serious head injury, facial injury and fatal head injury. The reduction was greater for serious or fatal head injury. Neck injury was rare and not associated with helmet use. These results support the use of strategies to increase the uptake of bicycle helmets as part of a comprehensive cycling safety plan."
A 2016 study from the Journal of Injury Epidemiology by Ruchi Kaushik and colleagues at the Mayo Clinic Children's Center. They studied data from a single county with no helmet law. ".. Of patients with head injuries, 17.4 % were documented to have been wearing a helmet, 44.8 % were documented as not wearing a helmet, and 37.8 % had no helmet use documentation. Patients with a head injury who were documented as not wearing a helmet were significantly more likely to undergo imaging of the head (32.1 percent vs. 11.5 %) and to experience a brain injury (28.1 vs. 13.8 %; p?=?0.008)." Of the most seriously injured: "Of the 500 patients who suffered head injuries, 11 required PICU admission or succumbed to their injuries. Of these 11 patients, 10 were not wearing a helmet and 1 had no documentation regarding helmet use."
A 2016 study from the American Journal of Surgery by Joseph Bellal MD et al:
Results: A total of 6,267 patients were included. About 25.1% of bicycle riders were helmeted. Overall, 52.4% of the patients had severe TBI, and the mortality rate was 2.8%. Helmeted bicycle riders had 51% reduced odds of severe TBI and 44% reduced odds of mortality. Helmet use also reduced the odds of facial fractures by 31%. "CONCLUSION: Bicycle helmet use provides protection against severe TBI, reduces facial fractures, and saves lives even after sustaining an intracranial hemorrhage."
A 2014 study from the American Journal of Public Health by Janessa M. Graves, PhD, MPH et al was the first to look at the effects of public bike share programs:
Results: "In PBSP cities, the proportion of head injuries among bicycle-related injuries increased from 42.3% before PBSP implementation to 50.1% after... Conclusions: Results suggest that steps should be taken to make helmets available with PBSPs. Helmet availability should be incorporated into PBSP planning and funding, not considered an afterthought following implementation."
And a 2013 study from Australia: The effectiveness of helmets in bicycle collisions with motor vehicles: A case-control study. This 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 2016 study in the International Journal of Epidemiology (1-15
doi: 10.1093/ije/dyw153) by Jake Olivier and Prudence Creighton: Bicycle injuries and helmet use: a systematic
review and meta-analysis. This study included 40 studies were in the
meta-analysis with data from over 64 000 injured cyclists. For cyclists involved in a crash or fall, helmet use was associated with odds reductions for head [OR¼0.49, 95% confidence interval (CI): 0.42–0.57), serious head (OR¼0.31, 95% CI: 0.25-0.37), face (OR¼0.67, 95% CI: 0.56-0.81) and fatal head injury (OR¼0.35, 95% CI: 0.14-0.88). No clear evidence of an association between helmet use and neck injury was found (OR¼0.96, 95% CI: 0.74-1.25).
Conclusions: Bicycle helmet use was associated with reduced odds of head injury, serious head injury, facial injury and fatal head injury. The reduction was greater for serious or fatal head injury.
A 2017 study from Traffic Injury Prevention by Jake Olivier & Igor Radun (2017): "Bicycle helmet effectiveness is not
overstated" discusses challenges in estimating bicycle helmet effectiveness from case-control studies, provide evidence that odds ratios using hospital controls likely underestimate helmet effectiveness, and proposes areas of further study.
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 website.
The Journal of Injury Prevention This 2003 study by P. L. Jacobsen is titled "Safety in numbers: more walkers and bicyclists, safer walking and bicycling." The author examined statistics for many countries and found that the more cyclists and pedestrians there are on the streets, the safer they all are. And an article in Berkeley's Planetizen newsletter in discusses other studies showing that pedestrians are safer as well. Riding in a place like the Netherlands or another location where there is lots of bike traffic will tell you that the thesis is correct, and these studies attempted to document it. Those who oppose helmet laws contend that the laws reduce cycling, thereby increasing the risk to each cyclist left on the streets. There is no evidence of that in the US.
Bicycle-associated head injuries and deaths in the United States from 1984 through 1988. How many are preventable?
Main results: "From 1984 through 1988, bicycling accounted for 2985 head injury deaths (62% of all bicycling deaths) and 905 752 head injuries (32% of persons with bicycling injuries treated at an emergency department). Forty-one percent of head injury deaths and 76% of head injuries occurred among children less than 15 years of age. Universal use of helmets by all bicyclists could have prevented as many as 2500 deaths and 757 000 head injuries, ie, one death every day and one head injury every 4 minutes."
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 very expensive 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.
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.
This study of ebike head injuries included 20 riders and pedestrians, all under 18. Seventeen of them had head injuries. None had been wearing a helmet. One died.
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 here.
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
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 back in 2004, before the current attention to concussion had begun. Although not a peer-reviewed journal article, it is available to the public for free, and is still 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." Although most bicycle riders do not suffer repetitive concussions, some do.
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 once available 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.
Cyclist head and facial injury risk in relation to helmet fit: a
case-control study calculates risk factors for helmets that fit poorly, and how much that they increase the risk of head and facial injury.
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 impact of bicycle helmet legislation on cycling fatalities in Australia: Olivier J, Boufous S, Grzebieta R. Int. J. Epidemiol. 2019; ePub(ePub): ePub.
This 2019 study concludes:
"RESULTS: Immediately following bicycle helmet legislation, the rate of bicycle fatalities per 1?000?000 population reduced by 46% relative to the pre-legislation trend [95% confidence interval (CI): 31, 58]. For the period 1990-2016, we estimate 1332 fewer cycling fatalities (95% CI: 1201, 1463) or an average of 49.4 per year (95% CI: 44.5, 54.2). Reductions were also observed for pedestrian fatalities; however, bicycle fatalities declined by 36% relative to pedestrian fatalities (95% CI: 12, 54).
"CONCLUSIONS: In the absence of robust evidence showing a decline in cycling exposure following helmet legislation or other confounding factors, the reduction in Australian bicycle-related fatality appears to be primarily due to increased helmet use and not other factors."
Two Australian studies have concluded that critiques of their helmet laws are bogus.
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. 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, Australian W. J. Curnow, feels that the data is stale and that helmets have changed. He says hard shell helmets are "rare" (they do have skate-style, downhill racing and 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. There was a rebuttal from two authors in Canada.
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.
Canadian parents' attitudes and beliefs about bicycle helmet legislation in provinces with and without legislation
P. C. Parkin, MD, et al.,Chronic Diseases and Injuries in Canada, Vol 34, No 1, February 2014. Concludes that "Parents are highly supportive of bicycle helmet legislation in Canada. They
believe that bicycle helmets are effective and that legislation does not decrease the
amount of time a child spends bicycling. There was also a high level of support for
legislation across all ages, and for police enforcement."
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 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 one of those under 18 who died as the result of a cycling collision was wearing a helmet. 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. Note that the original report had different numbers for those under 18.
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.
Would New Zealand adolescents cycle to school more if allowed to cycle without a helmet? Molina-García J, Queralt A, García Bengoechea E, Moore A, Mandic S. Journal of Transportation Health 2018; 11: 64-72. Attempts to answer the question with interviews of 774 adolescents. "Overall, 22.1% of adolescents stated that would cycle to school more often if helmet use was not mandatory." We are not sure what that proves scientifically, but that's what the kids said.
Liberty or Death; Don't Tread on Me A 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, Hynd, Cuerdon, Reid and Adams, 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 buses.
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.
Helmet Laws, Helmet Use, and Bicycle Ridership. A 2016 study of the effect of bicycle helmet laws on helmet and bicycle use among U.S. high school students in urban jurisdictions. Conclusions:
Laws increased helmet use in all jurisdictions, with limited evidence of reduced cycling. Although sound health policy, laws should be coupled with physical activity promotion.
The effect of an all-ages bicycle helmet law on bicycle-related trauma.
Kett P, Rivara FP, Gomez A, Kirk AP, Yantsides C. J. Community Health 2016; ePub(ePub): ePub.
This study looked at Seattle and King County stats before and after their all-ages helmet law. Conclusions: While the results do not show an overall decrease in head injuries, they do reveal a decrease in the severity of head injuries, as well as bicycle-related fatalities, suggesting that the helmet legislation was effective in reducing severe disability and death, contributing to injury prevention in Seattle and King County. The promotion of helmet use through an all ages helmet law is a vital preventative strategy for reducing major bicycle-related head trauma.
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.
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
Helmet use and injuries in children's bicycle crashes in the Gothenburg region (2017) Olofsson E, Bunketorp O, Andersson AL. Safety Sci. 2017; 92: 311-317. Analyzes children's injuries in Gothenburg between 1993 and 2006. "The adjusted odds of serious or more severe skull/brain injuries and moderate or more severe facial injuries with a helmet were about one fourth of those without a helmet. "
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.
Wearing a Bicycle Helmet Can Increase Risk Taking and Sensation Seeking in Adults. Walker, et al. Psychological Science. This study tracked people wearing caps or helmets while blowing up a virtual balloon on a computer screen. The researchers found that those in bicycle helmets took more risk that the balloon would burst, and concluded that "Here, we demonstrated that risk taking increases in people who are not explicitly aware they are wearing protective equipment; furthermore, this happens for behaviors that could not be made safer by that equipment. In a controlled study in which a helmet, compared with a baseball cap, was used as the head mount for an eye tracker, participants scored significantly higher on laboratory measures of both risk taking and sensation seeking. This happened despite there being no risk for the helmet to ameliorate and despite it being introduced purely as an eye tracker. The results suggest that unconscious activation of safety-related concepts primes globally increased risk propensity." There was some adverse reaction to the study, as there was to Walker's earlier study of passing clearances.
Wearing a bike helmet leads to less cognitive control, revealed by lower frontal midline theta power and risk indifference Schmidt et al, Institute of Psychology, Friedrich Schiller University of Jena, Germany. There is no pretense of scientific method in this study: "We hypothesized that wearing a bike helmet reduces cognitive control over risky behavior." It is not too surprising that their results proved what they had predicted. They were inspired by the study produced by Walker et al. (see above)
Risk Compensation - "a dead horse that no longer needs to be beaten"
Risk compensation: revisited and rebutted from Safety 2016, 2(3), 16; doi:10.3390/safety2030016
Barry Pless, Professor Emeritus, Pediatrics and Epidemiology, McGill University
Abstract: This Commentary addresses the ongoing disagreements between many safety advocates who endorse traditional models of prevention and those who oppose them, arguing that safety measures are offset by risk compensation (RCT). The debate is especially heated with respect to regulatory or legislative prevention measures. After explaining the rationale behind risk compensation (aka risk homeostasis theory) (RHT), I provide examples of RCT studies to explain why I believe they should be rejected. The main basis for my rebuttal, however, rests on data that show steady declines in unintentional injury mortality, which, according to RCT, should not have occurred. There are many other reasons for rejecting this theory, and it seems that the time has come for the debate to finally be concluded.
"Thus, perhaps the bottom line of this Commentary is 'enough said'; this is a dead horse that no longer needs to be beaten."
The full study is available without charge. It will surely not conclude the debate, but is a well-written critique of risk compensation theories related to helmets.
Is risk compensation threatening public health in the covid-19 pandemic? from British Medical Journal 370 doi: https://doi.org/10.1136/bmj.m2913 (Published 26 July 2020) Cite this as: BMJ 2020;370:m2913.
Eleni Mantzari, research associate Department of Public Health and Primary Care, Behaviour and Heath Research Unit, University of Cambridge, Cambridge, UK, and G James Rubin, Theresa M Marteau, professor, Department of Psychological Medicine, King’s College London, London, UK
Abstract: "Unfounded concerns about risk compensation threaten public health when they delay the introduction of protective measures such as wearing of face coverings..."
Based on COVID-19 research, but with general evidence about the bogus nature of risk compensation theories.
Bicycle helmets and risky behaviour: a systematic review:
Esmaeilikia M, Radun I, Grzebieta R, Olivier J. Transp. Res. F Traffic Psychol. Behav. 2019; 60: 299-310.
This systematic review on risk compensation found that:
"Eighteen studies found no supportive evidence helmet use was positively associated with risky behaviour, while three studies provided mixed findings, i.e., results for and against the hypothesis. For many of these studies, bicycle helmet wearing was associated with safer cycling behaviour. Only two studies conducted from the same research lab provided evidence to support the risk compensation hypothesis. In sum, this systematic review found little to no support for the hypothesis bicycle helmet use is associated with engaging in risky behaviour."
Helmets themselves and performance testing
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.
Helmets tested on and below the test line. MEA Forensic staff and others tested helmets above, on and below the test line. Some met the CPSC standard, but "The remaining six helmets failed to meet the criterion on and/or above the test line. Our findings indicate that consumers should not assume that all portions of a helmet provide adequate and equivalent protection. Our findings also suggest that the CPSC’s current system of self-regulation and self-testing by manufacturers does not prevent substandard bicycle helmets from being sold."
This Helmet Will Save Football. Actually, Probably Not.
This excellent NY Times article is deservedly skeptical about solving concussion and CTE problems in football with better helmets.
The effect of hair and football helmet fit on headform kinematics.
MEA Forensic has published a paper on their research showing that when a helmet slips on the head it reduces peak acceleration and peak angular acceleration. It is very likely that football helmets are more closely coupled to the head than a bicycle helmet due to their construction and additional coverage.
An analysis of energy management thickness for an anti-concussion helmet. Unpublished paper by Terry Smith and Dan Pomerening examining how thick an EPS foam helmet would have to be to pass the CPSC impact tests while keeping g's below 100.
3D assessment of damaged bicycle helmets and skull injuries. A study by G.J.C. van Baar et al used helmet scans and related the helmet damage to injuries suffered in the crash. They conclude that "Our proposed 3D method of assessing bicycle helmet damage and corresponding head injuries could offer valuable information for the development and design of safer bicycle helmets." The technique is likely to be used in forensic research for lawsuits.
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."
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.
RedOrbit: 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.
Influence of headform mass and inertia on the response to oblique impacts by Thomas A. Connor, Matt Stewart, Roy Burek & Michael D. Gilchrist (2018): International Journal of Crashworthiness, DOI: 10.1080/13588265.2018.1525859. Concludes that current headforms are poorly suited for studying helmet performance in oblique impacts. If you agree with the authors, studies of helmet performance using current headforms are unlikely to be valid.
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 reconstructions (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.
Helmet Add-Ons May Not Lower Concussion Risk in Athletes is a 2015 study of football helmet add-ons, including soft outer shells, spray treatments, pads and fiber sheets found that "there is no magic concussion prevention product on the market at this time."
Helmet design based on the optimization of biocomposite energy-absorbing liners under multi-impact loading
Based on finite element analysis and no lab testing this Portuguese study recommends the use of agglomerated cork for multi-impact helmets.
Assessment of the shock adsorption properties of bike helmets: a numerical/experimental approach Bocciarelli, Carvelli, Mariani & Tenni. (affiliated with MET helmets). "Laboratory compression and tensile tests were carried out on samples of expanded polystyrene (EPS) and polycarbonate (PC)...Finite element analyses of a helmet subject to standardized impacts ,,, allowed assessing the time evolution of the acceleration measured inside the headform (according e.g., to EN 1078)..."
This Google Scholar search found 28,000 scholarly links to bicycle helmet materials.
The European HOPE Study is not a journal article but a full-scale EU examination of helmets and their effectiveness. Nobody has ever done this before. The Final Report (2015) concludes:
There is much more in the report, including recommendations for changes in bicycle helmet testing standards.
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 and Bicycle 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.
- "..most bicyclists in Europe recognise the increased safety of wearing a helmet. However, they provide an extensive list of reasons why they still do not do so, including thermal discomfort."
- "The primary conclusion of this Working Group is that the full potential of bicycle helmets has not yet been fully exhausted. In fact, helmets could even provide additional benefits, when protection is extended further on the lateral side."
- "Working Group 1 is confident in its recommendation that increased usage of bicycle helmets can reduce the number and severity of head injuries."
- "While literature varies on the overall effectiveness of
bicycle helmets, the inconsistent usage and lack of data mean that absolute conclusions cannot yet be drawn about the overall impact of bicycle helmets on safety."