Fourteen studies were included (at least 10,605 children, range 11 to 1,778): three randomised controlled trials (RCTs) and 11 quasi-experimental/observational design studies.
The quality of all studies was rated as weak. Collectively the studies had problems with confounders, representativeness of samples and validity of outcome measures. Intervention integrity was inadequately reported and several studies did not account for school clustering or used inappropriate statistical methods for the study design.
Twelve studies reported a 3% to 64% increase in percentage of active transportation to school following the intervention. Two studies showed no difference.
Cohen’s d effect sizes were very small in three studies, small in six studies, large in two studies and very large in one study (Cohen’s d ranged from 0.071 to 2.9).