Strengths and limitations
This study had some limitations. Importantly, due to the COVID-19 pandemic, the full sample size was not attained, resulting in a lack of statistical power to detect differences between groups. Further, rising concerns regarding COVID-19 during the study period could have impacted on transport and physical activity behaviours. As such, this analysis was unable to draw firm conclusions about the findings, although these data provide some indication of a positive effect and help to inform future studies. COVID-19 also resulted in the abandonment of the planned further post-intervention (6-months) follow-up; thus, it could not be determined whether public transport behaviours would become a more normalised and integrated behaviour over time. The generalisability of this study to the broader population may be limited due to an over-representation of tertiary educated and female participants. The single-blinded design meant that study participants were aware of their group allocation (intervention or control). It must be noted that accelerometer and self-reported physical activity measures differed within this study. For example, it is possible that the control group’s increase in total self-reported physical activity and decrease in ambulatory steps/day is due to activity being undertaken that contributed to total physical activity levels that was not assessable by accelerometer (e.g., cycling, swimming, weightlifting, etc.). The outcomes of transport-related physical activity and total physical activity are prone to limitations due to their self-reported nature. While group allocation had not occurred at T1, participants were aware of their group at the T2 follow-up assessment, which may have biased reported activity levels. However, the use of accelerometers limit potential group allocation bias by providing an objective measure of activity for consideration alongside subjective self-report. There was potential for reactivity bias during the use of accelerometers to measure activity; However, the assessment of activity across a seven-day period and the analysis of the median steps/day over this period act to negate this potential bias. Further, as accelerometers were mailed to participants at T2 rather that administered face-to-face (as at T1), compliance with instruction of use may have been lower.A key strength of this study was its randomised and controlled study design. Further, its use of both objective and subjective measures of physical activity were important strengths. Accelerometers are an accurate and reliable objective measure of both step count and physical activity frequency, intensity, and duration [