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Mandatory helmet legislation and children's exposure to cycling

Macpherson AK, Parkin PC, To TM. Injury Prevention 2001;7:228-230

Summary of original paper
A mandatory helmet law for children was enacted in Ontario in October 1995. The study set out to examine trends in children's cycling rates before and after legislation in one health district. Child cyclists were counted at 111 preselected sites in the late spring and summer of 1993 - 97 and in 1999. Although the number of child cyclists per hour was significantly different in different years, the authors say that these differences could not be attributed to helmet legislation. In 1996, the year after the law came into effect, average cycling levels were higher than in 1995, the year before legislation (6.84 v 4.33 cyclists per hour). The authors therefore conclude that, contrary to the findings in Australia, the introduction of helmet legislation did not have a significant negative impact on child cycling in this community.

BHRF Commentary

Although the only paper producing such a result, and despite contradictory evidence from Australia, New Zealand and other jurisdictions where helmet laws have been introduced [2], this paper is often cited as evidence that helmet laws do not discourage cycling.

A letter pointing out serious shortcomings in the paper, together with the original author's reply, was subsequently published by Injury Prevention [1].

Read the full published critique here.

A principal criticism is that the Ontario law was not enforced. There is little data on the effect on cycling levels, although in one Toronto borough the proportion of child cyclists wearing helmets at first increased but then fell back to levels similar to that pre-law

As the law was not enforced, its deterrent effect on cycling was soon negated, and it did not significantly increase helmet use. The authors of the paper furnished no information about trends in helmet wearing by which to judge changes in cycle use.

Other criticisms include:

• The sample size was small and the survey limited to a single health district.
• The study excluded the age group most deterred by helmet laws (15 - 17 year olds).
• It is not clear that the data from successive surveys were comparable.
• There were large variations in children counted in different years which are not adequately explained. (The summer of 1999 was particularly sunny and may have boosted cycle use, but changes in such external variables have not been controlled for).
• Important data, such as helmet wearing rates, is absent.
• No adjustment has been made for population changes, yet the population of Ontario increased by 14% from 1988 to 1997.
• For a number of years starting in the late 1980's, the health district had been uniquely the object of a community driven helmet promotion campaign among children and therefore cannot be considered typical of the rest of Ontario.
• The authors are selective in the other research that they have referenced.

Postscript: Effect of Ontario law on head injuries
A later paper by the same authors showed that % head injuries to children had declined after enactment of the Ontario law and that therefore the law had been beneficial [3]. However, re-analysis of the data [4] showed that head injuries had started falling well before the law. Indeed, the greatest annual reduction had taken place 2 years before the law was enacted. After the law, the reduction in % head injuries was not significantly different to the situation in other Canadian provinces where cycle helmets were not mandatory. This suggests that trends, rather than helmet legislation, may have been responsible for the changes. This would not be surprising if the law had no significant lasting effect on either helmet or cycle use.

References

[1] Robinson DL. Helmet laws and cycle use. Injury Prevention 2003;9:380-381.
[2] see: How helmet promotion and laws affect cycle use.
[3] Macpherson AK, To TM, Macarthur C, Chipman ML, Wright JG, Parkin PC. Impact of mandatory helmet legislation on bicycle-related head injuries in children: a population-based study. 2002. Pediatrics: 2002; 110(5):e60.
[4] Robinson DL. Confusing trends with the effect of helmet laws. Pediatrics, post-publication peer review, July 2003.