Bicycling is a very popular pastime and mode of transportation for children. However, bicycling‐related injuries are common and frequently lead to hospitalisation or death. This is the case in high‐income countries and also in the developing world, where road traffic injury rates are highest and where a greater proportion of road users are cyclists.

In Canada 6% of all childhood injury‐related hospitalisations are caused by cycling incidents (CIHI 2004). This represents an annual hospitalisation rate of 52 per 100,000 with a mortality rate of six per 100,000 (Beaulne 1997). Similar mortality rates have been reported in the United States (Durkin 1999) and Australia (Acton 1995).

Head injuries in particular have serious consequences and account for 35 to 40% of paediatric hospitalisations and death due to bicycle related trauma (Beaulne 1997; Durkin 1999). Furthermore, bicycle‐related trauma has been reported among the most common causes of traumatic brain injury in many countries including Sweden (Peloso 2004), Taiwan (Tsai 2004) and the United States (Durkin 1999).

Bicycle helmets have been shown to be effective in preventing head, brain, and facial injuries to cyclists (Rivara 1998, Thompson 1996). A Cochrane systematic review reported that helmets reduce the risk of head injury by up to 88%, and reduce the risk of facial injury by 65% for cyclists of all ages (Thompson 2001).

However, despite the evidence of the efficacy of helmets in preventing serious injury, they are not universally used. Barriers to use include inhibitive costs, discomfort, lack of belief of necessity, and an unpopular image of helmets among young cyclists (Finch 1996; Finoff 2001).

In order to overcome resistance to helmet usage, legislation has been enacted in various parts of the world, including Australia, New Zealand, the United States, and Canada. Jurisdictions differ in the population range affected by legislation. In Australia, for example, bicycle riders of all ages must wear a helmet. In Canada, however, legislation applies to children and adolescents only. Enforcement of legislation also differs across jurisdictions as priorities for policing vary between states and countries.

Evaluations have shown that legislation is successful in increasing helmet use (Ni 1997; Dannenberg 1993; Cote 1992; Scheiber 1996; Foss 2000; Kanny 2001). However, few studies have focused on head injury as the primary outcome. The few studies that have evaluated changes in head injury rates have mostly used a time‐series design without a concurrent comparison group (Vulcan 1992; Scuffham 2000). Therefore, any reduction in head injury rates could be attributed to a general downward trend for reasons other than increased helmet use (Robinson 2001).

Without conclusive and scientifically sound evidence, the issue of helmet legislation remains controversial. Opponents of helmet legislation claim that children will use bicycles less if they are required to wear a helmet, and thus miss out on the health benefits and enjoyment that may be derived from cycling. One study published subsequent to the enactment of legislation in Australia supports this hypothesis (Robinson 1996). Others adhere to the risk compensation theory, claiming that helmeted riders ride more dangerously, and are at greater risk of injury (Hillman 1993; McCarthy 1993).

A systematic review of the highest level evidence is the first step to providing a clearer picture of the effectiveness of bicycle helmet legislation. If helmet legislation leads to a reduction in bicycle‐related head injuries, the public health benefits could be substantial. The current review will examine studies that have evaluated the effectiveness of bicycle helmet legislation for reducing head injuries in the whole population. The review will also examine studies that evaluate changes in helmet use, in order to assess enforcement across jurisdictions, and additionally those assessing the popularity of bicycling to gauge possible deterrent effects of legislation.