A systematic review of methods used to assess mandatory bicycle helmet legislation in New Zealand

BACKGROUND: Mandatory helmet legislation (MHL) for cyclists became effective in New Zealand (NZ) on 1 January 1994. Assessments of the NZ MHL have led to conflicting conclusions regarding its effectiveness at reducing cycling head injury and risk of fatality. These studies also differ in their use of analytic approaches and data sources. OBJECTIVES: The aim of this paper is to systematically review all studies that assess the NZ MHL in accordance with quality criteria for assessing population-based interventions. Data Sources: A search of Medline, Scopus and Web of Science for peer-reviewed articles from 1994 to 9 September 2014 was conducted. Study Selection: Documents were independently extracted by two reviewers and limited to original articles in peer- reviewed journals that assessed the NZ MHL in terms of cycling head injury. RESULTS: The results from three of the four included studies indicated a positive effect of MHL for increasing helmet wearing and reducing head injuries. However, the findings of these studies must be interpreted within the context of methodological limitations. CONCLUSION: We believe more high quality evaluations are needed to provide evidence for an objective assessment of MHL in NZ.