Two published studies and two other analyses have looked at the benefit-costs of cycle helmet legislation. Much of the analysis is, however, equally valid for helmet promotion outside the context of helmet laws.
In Australia the net benefit was found to lie in the range plus AUD 2 million to minus AUD 10 million (Hendrie, Legge, Rosman and Kirov, 1999). The decrease in cyclist head injuries was outweighed by the much greater reduction in cycle use.
A study in New Zealand found a large cost disbenefit for most helmet wearers (Taylor and Scuffham, 2002). Some benefit was reported for children under 12 years of age, but only by ignoring the helmet purchase costs for the large proportion of this age group that were already wearing helmets before the law was introduced.
A further analysis for New Zealand (BHRF, 1237) found no benefit at all from its helmet law. However, even on the most optimistic outcome, the costs arising from the law (principally the purchase of cycle helmets) hugely outweigh the very small healthcare costs that might be saved. See here for full details.
Johns, 2012 looked at the moral issues around the British Columbia bicycle helmet law as well as its benefit-cost. It was found that the benefits of the law would outweigh the costs only if the reduction in cycling brought about by the law was no more than 0.4% (moderate estimate of benefit) to 1.75% (most optimistic estimate of benefit). In practice the deterrent to cycling has been much greater than this and costs have much exceeded the benefits.
No benefit-cost analysis is known that has concluded unequivocally in favour of helmet promotion.
Robinson DL, . Costs and benefits of the NZ helmet law. .
Hendrie D, Legge M, Rosman D, Kirov C, 1999. An Economic Evaluation of the Mandatory Bicycle Helmet Legislation in Western Australia. Road Accident Prevention Research Unit .
Johns R, 2012. A cost-benefit analysis of BC's bicycle helmet law. Velo City Global, Vancouver 2012 .
Taylor M, Scuffham P, 2002. New Zealand bicycle helmet law - do the costs outweigh the benefits?. Injury Prevention 2002;8:317-320.