Physical activity from bus travel: objective estimates linking accelerometer and travel card data

Background Low physical activity contributes to chronic disease and premature death. Public transport can integrate activity into daily routines, but robust methods are needed to estimate physical activity during public transport trips. This study quantified duration, intensity, and steps taken during active travel bouts to bus stops by linking accelerometer data with transport smartcard-recorded bus boardings. Methods Participants (aged ≥ 15 years) from two Tasmanian trials of a financial incentives program to increase public transport use ( trips4health and Get BusActive! ) wore accelerometers for up to 7 days at three timepoints. Timestamped bus boardings were obtained from smartcard records. Active travel bouts to bus stops were identified using a time-based linkage window and bout intensity was classified using Freedson cut-points. Mixed-effects models estimated bout duration and steps, accounting for repeated measures within individuals. Results 298 participants completed 1396 bouts to bus stops. Most bouts (93%) were of moderate intensity. On average, bouts lasted 6.8 min (95% confidence interval [CI] = 6.6, 7.1) and comprised 473 steps (95% CI = 445, 502). Estimates were robust to alternative assumptions. There were no differences by study, treatment group, or timepoint. Assuming similar access and egress activity, round-trip bus use on four days per week could contribute ∼75% of recommended physical activity for adults. Conclusion Walking to and from public transport stops can contribute to meeting physical activity guidelines. Further studies across settings and transport modes are needed to inform health impact modelling, targeted interventions, and public health messaging.