Methodological quality of included studies Study quality was assessed using a tool developed by Thomas and colleagues25,26 recognized as being suitable for use with both randomized and non-randomized studies. Meta-analysis was not attempted due to marked heterogeneity of study designs, interventions, outcome measures and analytical approaches among the included studies.27 We followed the Cochrane handbook guidance supporting the use of a systematic, narrative approach when meta-analysis is inappropriate, 28 and synthesized the study results according to study design and the environmental explanatory variables assessed (e.g. trip distance, provision of cycle lane).