Wong et al. BMC Public Health 2011, 11:618 http://www.biomedcentral.com/1471-2458/11/618 School transport considerations will be integral to the success of such interventions. Conclusions In summary, our findings demonstrate that the preva- lence of active school transport varies across time and region. Similarly, the correlates of school transport vary across time and age groups. Future research examining school transport should continue to make the analytic distinction between the morning and afternoon trip, and control for the moderating effect of age and geography in predicting mode choice. List Of Abbreviations AST: Active school transport; CDC: Centers for Disease Control and Prevention; OSDUHS:Ontario Student Drug Use and Health Survey Acknowledgements and funding This research was funded by the Built Environment, Obesity and Health Strategic Initiative of the Heart and Stroke Foundation and the Canadian Institutes of Health Research (CIHR). OSDUHS is funded in part by ongoing support from the Ontario Ministry of Health and Long Term Care. We would like to thank all of the schools and students that participated in the study and the Institute for Social Research at York University for assistance with the survey design and data collection. Author details 1Faculty of Physical Education & Health, University of Toronto, 55 Harbord Street, Toronto, Ontario, M5S 2W6, Canada. 2Department of Geography, University of Toronto at Mississauga, 3359 Mississauga Road North, Mississauga, Ontario, L5L 1C6, Canada. 3Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5S 2S1, Canada. Authors’ contributions BYW analyzed and interpreted the data and developed the first draft of the manuscript. GF and RB contributed to the conception and the design of the study. HI contributed to the analysis of the data. All authors provided critical feedback during manuscript development. 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