The review concluded that interventions showed a small but promising effectiveness in increasing active transportation to school but there were limitations with the included studies and further research was needed. The quality of the evidence base and differences across studies limited the reliability of the results and the authors’ cautious interpretation of the evidence seems appropriate.

To review intervention studies related to active school transportation to guide future intervention research.

PubMed, SPORTDiscus, Web of Science, The Cochrane library and National Transportation Library were searched to January 2010 for articles in English. Search terms were reported. Reference lists of published articles and reviews were searched.

Studies of active transportation to school interventions in children or adolescents (aged six to 18 years) were eligible for inclusion. Studies had to report on at least one outcome or indicator of active transportation or physical activity.

The included studies considered active transportation to school interventions which included elements of preparation, promotion, programs, projects and/or policy strategies. Most studies used parental-reported and/or child-reported frequency of child walking and biking to school. The age range of the children was five to 15 years. Study duration ranged from four weeks to four years. Most studies were conducted in elementary schools; one study was in middle school. Studies were conducted in USA, Australia and UK. Most studies were in urban settings.

More than one reviewer was involved in study selection. Disagreements were resolved by discussion.

Quality assessment was undertaken using a modified Evaluation of Public Health Practice Projects for selection bias, study design, confounders, blinding, data collection methods, withdrawals and drop-outs, integrity and statistical analysis. Studies were graded as weak, moderate or strong evidence.

Two reviewers were involved in quality assessment and a third reviewer was used as an adjudicator where needed.

Data were extracted on outcomes of active transportation or physical activity and used to calculate effect sizes between groups or between baseline and follow-up. Effect sizes were expressed as Cohen’s d and ranked as very large effect (Cohen’s d>1.3), large (>0.8), moderate (>0.5), small (>0.2) and very small (≤0.2).

Data were checked by two reviewers and disagreements were resolved by discussion with a third reviewer.

A narrative synthesis was undertaken.

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).

Interventions showed a small but promising effectiveness in increasing active transportation to school but there were limitations with the studies and further research was needed.

Inclusion criteria for the review were clearly defined. Several relevant data sources were searched. Only articles in English were included so there was potential for language bias. Publication bias was not assessed and could not be ruled out. It appeared that more than one reviewer was involved in the review processes to minimise reviewer error and bias. Quality assessment indicated that the quality of the evidence base was weak.

The authors noted that there were differences across the studies in terms of scope, size and focus of the interventions and outcomes. Data were narratively synthesised and effect sizes were calculated.

The quality of the evidence base and differences across studies limited the reliability of the results and the authors’ cautious interpretation of the evidence seems appropriate.

Practice: The authors stated that interventions with appropriate school, parent and community involvement and that worked toward a specific goal seemed to be more effective than interventions with a broader focus.

Research: The authors stated that future studies should examine the effect of the parental, school and community involvement influence on active transportation to and from school. The complexity of multiple factors should be considered. Long-term outcomes and the sustainability of active transportation to school interventions should be examined. From a methodological perspective, schools should be used as a unit of randomisation to avoid contamination between groups within a school receiving different interventions, a theoretical framework should be used, valid and reliable outcome measurement tools should be employed and appropriate statistical analysis should be utilised.

One author was funded by the Spanish Ministry of Education.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.