CPSC Study: Bicycle Injuries and Helmet Use
Summary: CPSC's 1994 study of bicycle injuries and helmet use
U. S. Consumer Product Safety Commission
Washington DC
June, 1994
Excerpts from the Summary of
Bicycle Use and Hazard Patterns
in the United States
Prepared by Gregory Rodgers
Note: Although we respect Greg Rodgers as a competent economist, we are highly skeptical of the surveys used
to gather the data on which this study is based. So is John Allen, who has published a critique. In 2001 the New York Times published bogus conclusions on helmet effectiveness based on this study.
Helmet sections only!
snip.....
Bicycle riding is also a risky activity, as indicated by the large numbers of injuries and deaths involving bicycles
every year. According to the U.S. Consumer Product Safety Commission's (CPSC) National Electronic Injury Surveillance
System (NEISS), an injury reporting system that consists of a statistical sample of the nation's hospital emergency
rooms, there have been about one-half million nonfatal bicycle-related injuries treated in hospital emergency rooms every
year since the early 1970s, when NEISS became operational. When other medically-attended injuries are counted, such as
injuries treated in physicians' offices, there may be on the order of one million medically-attended injuries involving
bicycles every year. In addition, there are as many as 1,000 bicycle-related fatalities annually. The estimated costs of
these injuries and deaths to society are high -- approximately $8 billion annually -- and suggest that injury reduction
strategies with even modest levels of effectiveness could prove to be cost-effective.
Bicycle Helmet Findings
While recent studies show substantial safety benefits from helmet use, they also reveal that only a small proportion of
riders actually use helmets. The exposure survey provides valuable insights into current helmet usage patterns and on the
reasons why riders use or do not use helmets. This section summarizes the helmet usage patterns of bicyclists and the
statistical analysis of factors associated with helmet use, which are detailed in Part II. It also describes the attempt
in Part III to evaluate the impact of helmet use on the likelihood of head injury.
Descriptive Results
The exposure survey found that only 11.8 million (18 percent) of the entire population of about 67 million bicyclists
wear helmets all or most of the time. Another 6 percent, representing about 4 million riders, reported that they wear
helmets sometimes, but less than half of the time.
The proportion of children under age 15 who wear helmets all or most of the time was about 15 percent. HF reports (in
Part IV) that the low usage rate for children may be partly related to peer pressure. Some studies show that children are
not inclined to wear helmets if their social group disapproves of helmet use. However, helmet use in all age groups
appears to be increasing. Just over half of the current users (53 percent) began wearing helmets in the last two
years.
(Footnote: The Rodale Press findings for adults, described in Part VII, were similar. In 1990, only about 15 percent of
adult bicyclists wore helmets all or some of the time. However, the results also suggested that helmet use was likely to
increase substantially. About 10 percent of riders who did not own helmets said they planned to buy one within 2 years.
If plans materialized, helmet usage rates would have increased to about 25 percent by 1992.)
Nearly all of the 9 million riders who always wear helmets described "safety" as an important reason for doing
so. The "insistence of family members," was also important to about half of those who always wear helmets.
Usage patterns for 6.8 million riders who wear helmets sometimes, but not all of the time, are apparently affected by
risk perceptions. Many said that they usually wear helmets when in traffic (40 percent) and when on long rides (25
percent). Many also reported that they are less likely to wear helmets when riding only a short distance and when not
riding in traffic.
Finally, when non-helmet users were asked why they do not wear helmets, nearly half (48 percent) reported that they had
never considered wearing helmets, 21 percent said helmets were unnecessary, 19 percent said they did not wear helmets
because they seldom ride in traffic, and 16 percent said they had not gotten around to wearing them.
Helmet Use Patterns
In an analysis of factors associated with helmet use, the exposure survey data revealed that
the likelihood of helmet use increases with the amount of riding time. It is higher for those who ride on major
thoroughfares and bike paths, and is lower for those who ride on neighborhood streets and on sidewalks and playgrounds.
The relationship between age and helmet use is more complex, suggesting that helmet use increases with age for frequent
riders and declines with age for infrequent riders. The results also suggest that children age 10 and under are more
likely to wear helmets, relative to older riders, than can be otherwise explained by the general relationship between age
and risk. The likely explanation is that enough parents of young children require their children to wear helmets so that
helmet use patterns of children are distinguished from those of older bicyclists. Helmet use also increases substantially
with higher household education levels.
These relationships are illustrated for individual riders in a table at page 53. For example, consider a male who rides
300 hours per year on neighborhood streets, and who has (or, for children, whose parents have) no more than a high school
education. The expected likelihood of helmet use decreases from 9.9 percent for a 10 year-old rider to 6.8 percent for a
20 year-old rider. However, it rises again to 10.5 percent for a 40 year-old rider. In contrast, for a 30 year-old female
who rides about 50 hours a year on
neighborhood streets, the likelihood of helmet use rises from 5.4 percent if she has a high school education, to 16.4
percent if she has a college education. It rises further to 37.1 percent if she not only has a college education but also
rides primarily on major thoroughfares.
The analysis of the Rodale Press survey data on helmet usage patterns (in Part VIII) came to similar conclusions. Helmet
use increased with riding distances, and was higher for bicyclists who ride primarily on major thoroughfares and off-road
trails. In addition, helmet use increased with household income, a variable not included in the analysis of helmet use
patterns from the exposure survey.
Helmet Effectiveness
Since helmets are intended to reduce the likelihood of head injury, EP used injury survey data to examine the safety
effects of helmet use by estimating the conditional probability of head injury given that a helmet was worn. As described
in Part III, the results of this analysis were inconclusive, probably because the sample of helmet users was small (only
about 12 percent of the injured riders were wearing a helmet at the time of accident), and possibly because no
information was available on riders who avoided injuries or whose injuries were less severe because they were wearing
helmets.
However, EP found evidence that helmets prevented or reduced the severity of some head injuries. Helmets were damaged in
16 of the injury cases, about one-third of the cases in which they were worn. In 11 of these cases (69 percent), the
victim did not sustain a head injury. In addition, in all 16 cases, the victim expressed the opinion that the helmet
prevented a head injury or made it less severe.
Conclusions and Implications for Injury Reduction
...snip...
Head injuries represent the most serious and potentially life threatening injuries that can be sustained by bicyclists.
According to the injury survey results, almost one-third of hospital emergency room treated injuries involve the head,
and children under age 10 are significantly more likely than older riders to suffer head injuries. In addition, Sacks et
al. (1991) estimate that about 62 percent of all U.S. bicycle-related deaths involve injuries to the head. Based on these
estimates, the societal costs associated with the bicycle-related injuries and deaths involving head injury amounted to
more than $3 billion in 1991. Available evidence indicates that helmets reduce both the likelihood and severity of head
injury (Dorsch et al, 1987; Thompson et al., 1989). Results from the exposure survey, however, indicate that only about
17.6 percent of bicyclists currently wear helmets. This is higher than the 5 to 10 percent usage rate estimated in
studies conducted only a few years ago (see references at Part II), and suggests that attitudes towards helmet use are
improving. Nevertheless, helmet usage rates remain low. Increasing helmet use may therefore be the single most important
factor in reducing the incidence of serious bicycle injuries.