Table 1 Limitations of current work on AM and PA and how PASTA will address these (adapted from Gerike R, et al: Physical Activity Through Sustainable Transport Approaches (PASTA): A study protocol for a multi-centre project, forthcoming)

Few multi-centre studies in Europe with comparable research designs.

One study design is applied in seven PASTA cities (Antwerp, Barcelona, London, Oerebro, Rome, Vienna, Zurich).

Most studies on correlates of AM are cross-sectional.

Longitudinal approach, online survey with long baseline questionnaire and frequent short follow-ups, continuous recruitment over two years.

Often small sample sizes.

Targeted sample size of 14000 respondents across seven cities, number of submitted questionnaires per city > 5000.

Current studies are conducted either with methods from public health (over-simplified picture of travel behaviour, no motorised trips) or from transport research (no leisure time PA, proportion of recreational PA in leisure trips unclear).

PASTA takes an interdisciplinary approach with a systematic combination of methods from public health (modified GPAQ) and transport research (travel diary) for comprehensive data collection on AM and PA.

The relative importance of various correlates of individual AM behaviour is poorly understood, few studies comprehensively assess the wide range of factors which affect AM and PA.

Data collection and analysis based on a broad conceptual framework reflecting geographical, utilitarian and psychological factors, as well as data hierarchies (aggregation levels).

Contextual factors are usually not taken into account in quantitative analyses.

Systematic combination of qualitative and quantitative methods, with a major longitudinal web-based survey, expert interviews, stakeholder workshops, compilation of city indicators on AM, PA, and contextual factors. Qualitative data is integrated in quantitative analyses.

Substitution behaviour is poorly understood.

Multiple, repeated parallel assessments of AM and PA allow for quantification of substitution behaviour in the short and longer term. We will advance the field by also using real tracked data [50].

Few studies exist on the evaluation of AM measures.

Evaluation of top measures in the PASTA cities - infrastructure investments and built environment changes, such as bicycle racks and a dedicated cycling bridge; soft measures such as workplace mobility management and individual marketing.

Self-reported estimates of PA and AM are often not validated.

Validation of self-reported data on levels of PA and AM on subsamples collecting objective data using accelerometers, smartphone tracking apps, GPS loggers.

Lack of real-life studies on combined health effects of air pollution and PA – especially multi-centre studies are missing.

In three cities, exposure to air pollution and PA is assessed under real-life conditions. A multitude of non-invasive health biomarkers are repeatedly measured in 120 volunteers.

Air pollution exposure while traveling is largely unknown or ignored by using fixed monitoring stations.

Mobile sensors are used for air pollution, PA and travel behaviour. Not only exposure, but also inhaled dose is taken into account (especially relevant for AM).

Underreporting of minor AM crashes and near misses.

Integration of questions about AM crashes and near misses into the core module of the PASTA longitudinal survey.

Crash risk for walking and cycling is based on cross-sectional counts of fatal/reported accidents.

Exposure-adjusted crash risk (including near misses) using a longitudinal study design.