Table 1 General descriptions of the included studies

Reference, year	Country	Cyclist population	Design	Definition of correct helmet use
Finch et al,14 1993	Australia	All rider ages	Observational survey	Helmet’s chin strap fastened
Forjuoh et al,9 2002	USA	All children	Cross-sectional, direct observation	Positioned on head in a straight, horizontal line, strapped visibly below chin
Hall et al,13 2004	Australia	Elementary schools	Randomised controlled trial evaluating intervention	Fastened straps, positioned squarely on the head, cap not worn under helmet, correct helmet size
Harlos et al,11 1999	Canada	All rider ages	Observational survey	Visual assessment of fit, positioning on head, and appropriate strap use
Nykolyshyn et al,1 2003	Canada	All rider ages	Observational cohort survey	Sit level with rest of head, bottom of helmet ∼2 finger widths away from top of rider’s eyebrows, helmet straps fastened with ∼1 finger width space between chin and straps
Parkinson et al,10 2003	USA	All children	Questionnaire/helmet fit and condition assessment	Condition, room, strap, stability
Rivara et al,7 1999	USA	Helmeted subjects	Case–control (questionnaire, head/helmet measurement)	N/A
Rowe et al,3 1995	Canada	All rider ages who stopped and agreed to participate	Prospective roadside survey	Helmets should sit on forehead (not over eyebrow, should not expose forehead); straps should be “snug”; should remain in place when movement is attempted
Thompson et al,15 1997	USA	Injured cyclists	Case–control (self-report/expert evaluation)	Incorrect: poor fit, improper helmet placement because of style or fit, helmet failure when energy exceeds the threshold of ultimate protective capacity, impact occurring outside of covered head area
Twomey et al,8 2001	USA	All rider ages	Observational survey	Incorrect: helmet worn too far back on the head (forehead not covered) or without buckle fastened
Van Houten et al,16 2007	USA	Elementary school	Observational survey of baseline and treatment conditions	Helmet buckled snugly, level (forehead or back of head not exposed)

N/A, not applicable.