There is a summary statement available based on an earlier version of a broader review by the same author Royal et al. (2005), for the Cochrane Library, that includes some of the outcomes addressed in this 2007 review. The Cochrane review has since been updated, and an updated summary statement is forthcoming. See the section below: "This review is also published elsewhere."

OBJECTIVES: To assess the effectiveness of non-legislative interventions in increasing bicycle helmet use among children and young people, and to identify possible reasons for differential effectiveness of interventions. This paper reports an update to a 2005 review published in the Cochrane Database of Systematic Reviews.
DESIGN: Systematic review and meta-analysis.
DATA SOURCES: 10 electronic databases were searched up to October 2006. Several other sources of potentially relevant information were identified and examined.
REVIEW METHODS: We included randomized controlled trials, non-randomized controlled trials and controlled before-and-after studies of interventions to promote bicycle helmet use, which did not require the enactment of legislation. Participants were aged between 0 and 18 years.
MAIN OUTCOME MEASURE: Observed helmet wearing.
RESULTS: 13 studies were included in the review and 11 in the meta-analysis. The odds of observed helmet wearing were significantly greater among children and young people in the intervention groups (OR 2.13, 95% CI 1.35 to 3.35). Subgroup analysis indicated that the effect might be greater for community-based studies (4.57, 2.37 to 8.81) and those providing free helmets (4.60, 2.25 to 9.43) than for those providing subsidized helmets (2.11, 1.09 to 4.06) and those set in schools (1.73, 1.04 to 2.89). Evidence for the effectiveness of the interventions was stronger in studies with follow-up periods of CONCLUSIONS: Non-legislative interventions are effective in increasing bicycle helmet use among children and young people. Community-based helmet promotion programmes that include the provision of free helmets may increase observed helmet wearing to a greater extent than those set in schools or those providing subsidized helmets.