Measurement and patterns of active commuting

Despite 85% of the sample having access to a car, active commuting was a highly prevalent behaviour in our cohort, reflecting the local background prevalence of cycling and the selection of largely healthy workers into the cohort. We used synchronous household travel diary and georeferenced combined heart rate and movement sensor data to validate our primary outcome measure of time spent in active commuting derived from the core questionnaire, finding relatively small mean differences between the self-reported and objective estimates for cycling (1.12 minutes per trip) and walking (2.37 minutes per trip). Although time spent in physical activity overall changed little over the duration of the study, the median weekly time spent in active commuting declined from 120 minutes to 100 minutes (p = 0.001), mostly explained by a decrease in time spent cycling.

Relationships with physical activity, health and wellbeing

Walking and cycling were often incorporated into longer commuting journeys made predominantly by car or public transport. We used the sensor data to estimate the physical activity energy expenditure associated with specific travel patterns such as using buses or park-and-ride facilities. On average, 20% of the duration of these ‘multimodal’ trips was spent above the moderate physical activity intensity threshold, indicating their substantial potential contribution to commuters’ overall weekly physical activity. Those who spent more time in active commuting were more likely to record higher levels of overall physical activity as measured by accelerometer, and reported higher levels of physical well-being.

Role of social factors

Commuting practices were complex and shaped by a multitude of social commitments that were liable to change. People ultimately adopted the travel patterns that were most compatible with these commitments and imposed the least burden on themselves and their families. At the same time, both qualitative and quantitative analyses corroborated a hypothesis that participants’ life stage and socioeconomic circumstances influenced how far they lived from the city centre, which in turn affected their commuting behaviour. Social context thus shaped commuting practices not only through changeable social ties, but also through broader socioeconomic patterns. Commuters did not necessarily regard travel time as wasted time, and their journeys could give rise to both positive and negative experiences that were also important in shaping travel patterns.

Role of environmental factors

We confirmed that distance between home and work was an important influence on commuting behaviour, but we also showed that distance need not present an obstacle to incorporating substantial quantities of walking or cycling into longer journeys made by car or public transport. Some perceived and objective features of the environment were associated with active commuting in cross-sectional analyses, and with the uptake or maintenance of active commuting in complementary longitudinal analyses. The latter provided important new evidence that interventions aiming to provide safe, convenient routes for walking and cycling and convenient public transport – such as the busway – might be expected to promote active commuting. They also identified a strong influence of the provision and cost of workplace parking, suggesting new targets for intervention and evaluation in future studies. These hypotheses were further supported by qualitative research showing that people moving home or workplace were primarily motivated by considerations of convenience, speed, cost and reliability when deciding how to make their new journey to work.

(In the report we present a fuller exploration of different ways of capturing key constructs of importance to the study. This illustrates how the choice of method can influence not only the practicality of measurement but also the inferences that may be drawn, for example about the correlates of physical activity or the characteristics of commuting routes. Our subsequent evaluation of the busway, therefore, drew on findings using different types of data, analysed from a variety of perspectives, to draw robust and meaningful conclusions about its effects.)

Evaluating new transport infrastructure

Contextualising and interpreting the effects

Interviews suggested that although people were unlikely to use the new infrastructure unless it closely matched the journeys they needed to make, a range of other factors informed travel behaviour, and these were dependent on the value attributed to different aspects of the journey experience. These generally involved considerations of comfort, ambience or pleasantness and of feeling safe, which could trump considerations of reliability and speed. Although experiences of the busway were complex and ambiguous, they culminated in meaningful travel behaviour change for some users, through shifts in the balance between influential factors and planning, trialling and adopting new practices over time.

Linking active commuting with health benefits

We found no direct evidence of an effect of the intervention on time spent in physical activity overall, but the study lacked statistical power to detect such an effect. However, we found no compensatory decrease in recreational physical activity, and in observational cohort analysis changes in active commuting were associated with commensurate changes in total self-reported physical activity. Cycle commuting was also associated with lower sickness absence at work and improved well-being and weight status 1 year later, albeit with modest effects at the individual level.