Do helmet laws cost society more than they are worth?
Summary: A paper published by Dr. Piet de Jong in March of 2009 attempts to convince people that
helmet laws reduce cycling and are therefore a net detriment to public health. The paper presents a model quantifying the
cost to society of helmet laws, using exercise as the health benefit and injuries as the health cost. We think the model
is based on false assumptions that laws reduce cycling, and the results are not valid.
Dr. Piet de Jong of Macquarie University in Australia has published a paper titled Evaluating the Health Benefit of Bicycle Helmet Laws
This is the first part of the abstract:
A model is developed which permits the quantitative evaluation of the benefit of bicycle helmet laws. The efficacy of the
law is evaluated in terms of the percentage drop in bicycling, the percentage increase in the cost of an accident when
not wearing a helmet, and a quantity here called the "bicycling beta." The approach balances the health benefits of
increased safety against the health costs due to decreased cycling. Using estimates suggested in the literature of the
health benefits of cycling, accident rates and reductions in cycling, suggest helmets laws are counterproductive in terms
of net health...
Dr. de Jong is a Professor of Actuarial Studies, and the Head of Department for Macquarie's Department of Actuarial
Studies, so his work can be taken seriously. It is scholarly and scientific in tone. But the premises he bases his
analysis on are the familiar anti-helmet law refrains we have heard and disagreed with for many years. Our response point
- From our observation, from local reports and from talking to many cyclists about local riding numbers we have seen
no evidence in the US that a helmet law has ever caused a drop in bicycling. Here as in most countries, bicycling rises
and falls with weather, seasons, fashion, extreme gas prices and our heroes performing well in the Tour de France, but
in the years since our first helmet law as adopted in 1990 there has never been an abrupt change in cycling when a
helmet law was passed.
- If there were a reduction in cycling, there is no evidence in the US or anywhere else that a drop in cycling
automatically means a drop in exercising. De Jong's analysis assumes that cycling is the only form of exercise
available, so riders who stop riding automatically degenerate into couch potatoes. In fact, any cyclist who wants to
exercise but hates helmets enough to quit cycling if a law is passed can turn to a multitude of other activities to
- Helmetless crashes do produce higher medical costs, and higher costs to society caring for the uninsured.
- Environmental effects again are not changed here by a helmet law. Helmet laws here do not motivate people to drive
their cars. Most cyclists in our society have a car and use it for at least some activities. Helmet laws do not change
- The author says that he used "empirical estimates using US data" to determine the cost of a US national helmet law.
Although he introduces and manipulates data, that is not actually possible, since the word empirical means "derived
from experiment and observation rather than theory." Empirical data do not exist here to determine even the most basic
elements of bicycle usage. We just do not gather that data in our diverse society, and estimates of the number of
cyclists or annual cycling per person in the US are wild guesses based at best on telephone sampling. So are the
estimates of helmet usage, with a few local exceptions based on actual field observation. We have good numbers on
fatalities, but not on total crashes or injuries. The paper's estimates for the US are therefore baseless, even if you
agree with the methodology.
After presenting his equations, Dr. de Jong says that even if his formula suggests a net benefit from helmet laws,
there are other factors not found in the formula that would decrease it. He then lists five of the standard legacy
anti-helmet law arguments. We have a longstanding page on helmet law opposition
all of those points.
The paper notes that "even if an analysis suggests that there is no net societal benefit of a helmet law, it may still
make eminent sense for individuals to wear a helmet."
Dr. De Jong's model dresses up traditional anti-helmet law arguments in a more sophisticated presentation. But formulae
do not yield valid results if the basic assumptions are not correct. We found the abstract of this paper misleading. If
you are interested it may be worthwhile for you to read the full paper
and judge for yourself.