Butting heads over bicycle helmets
==================================

* Mary L. Chipman

John LeBlanc1 actually reinforces my concern that the number of cyclists has decreased after bicycle helmet legislation.2 His study was designed to maximize the number of cyclists observed in a fixed time interval, and he chose sites and circumstances accordingly. However, despite this effort to observe more cyclists, he actually observed fewer after legislation, so I am quite convinced that the number of cyclists has been dropping. I noted in my commentary that part of the explanation might be variation in sites and weather, and I thank LeBlanc for confirming this.

I am chided for not quoting from an article by my Toronto colleagues.3 To the best of my knowledge, my copy of the journal in which the article was published arrived after I had written and submitted the commentary. Now that I have had a chance to include this material, I note that the major component of the increased use that impressed LeBlanc was off-street cycling in schoolyards and parks, where rates of use more than doubled to over 10 cyclists per hour. Rates on streets and at major intersections either remained the same or increased in this interval to 5.4 per hour. Changing where children cycle is one response to the increasing concern about road safety; however, such an option may not be available for the many adult cyclists who commute.

LeBlanc claims that his results cannot be used as evidence that cycling decreased after legislation was introduced. I agree that the results cannot explain why the number of cyclists was lower at the 2 observation times after legislation. However, his data do indicate that the numbers dropped quite dramatically. This is consistent with an unfortunate and unintended side-effect of legislation, but may be only part of the explanation.

DeMarco looks at the longer-term consequences of having fewer cyclists on the roads, both in the cardiovascular health of cyclists and the risk of injury. With a decrease in cyclists on the roads, he foresees greater risk of heart disease and increased risk of injury if the environment becomes increasingly hostile to isolated cyclists. With such a short interval of observation, LeBlanc and colleagues can neither confirm nor deny such hypotheses.

**Mary L. Chipman** Department of Public Health Services University of Toronto Toronto, Ont.

## References

1.  1. LeBlanc JC, Beattie TL. Culligan C. Effect of legislation on the use of bicycle helmets. CMAJ 2002;166(5):592-5.
    
    [Abstract/FREE Full Text](http://www.cmaj.ca/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6NDoiY21haiI7czo1OiJyZXNpZCI7czo5OiIxNjYvNS81OTIiO3M6NDoiYXRvbSI7czoyMDoiL2NtYWovMTY3LzQvMzM5LmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ==) 

2.  2. Chipman ML. Hats off (or not?) to helmet legislation [editorial]. CMAJ 2002;166(5):602.
    
    [FREE Full Text](http://www.cmaj.ca/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiRlVMTCI7czoxMToiam91cm5hbENvZGUiO3M6NDoiY21haiI7czo1OiJyZXNpZCI7czo5OiIxNjYvNS82MDIiO3M6NDoiYXRvbSI7czoyMDoiL2NtYWovMTY3LzQvMzM5LmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ==) 

3.  3. Macpherson AK, Parkin PC, To TM. Mandatory helmet legislation and children's exposure to cycling. Inj Prev 2001;7(3):228-30.
    
    [Abstract/FREE Full Text](http://www.cmaj.ca/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MTA6ImluanVyeXByZXYiO3M6NToicmVzaWQiO3M6NzoiNy8zLzIyOCI7czo0OiJhdG9tIjtzOjIwOiIvY21hai8xNjcvNC8zMzkuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9)