Safe Routes to School (SR2S) interventions have been implemented in many economically developed countries to improve children's engagement in Active School Travel (AST). Evaluations have highlighted inconsistencies in SR2S intervention outcomes, raising questions as to how, why, and under what contextual conditions these interventions work. This review used a Rapid Realist Review (RRR) methodology to build, test, and refine an overarching program theory that unpicks the contextual factors and underlying mechanisms influencing children's engagement in AST. From the 45 included documents, 16 refined Context-Mechanism-Outcome Configurations (CMOCs) were developed and clustered into three partial program theories (i.e., implementor/implementation, child, and parent), with the associated mechanisms of: (1) School Reliance; (2) School Priority; (3) Fun; (4) Pride; (5) Perceived Safety; (6) Distrust; (7) Convenience; (8) Perceived Capabilities; and (9) Reassurance. The overarching program theory delineates the pathways between intervention implementation, children's motivation, parental decision-making, and children's engagement in AST. The findings suggest SR2S interventions can motivate children to engage in AST, but whether this motivation is translated into engagement is determined by parental decision-making. This review is novel for highlighting that many of the factors influencing parental decision-making are contextually driven and appear to be unaddressed by the current suite of SR2S intervention strategies. The review additionally highlights the complexity of parental perceptions of safety, with the traffic and the road environment shaping only part of this multidimensional mechanism. Practitioners and policymakers need to tailor SR2S interventions to local contexts to better influence parental decision-making for children's engagement in AST.
Keywords: Active School Travel; Rapid Realist Review; Safe Routes to School; active school transportation; children; interventions; physical activity.