Undertaking mobility field experiments using GPS tracking

The world we live in is increasingly digital. In only the last decade, the humble mobile phone has developed into a powerful portable computer carried in the pockets of almost the entire population. The integration of GPS-receivers into these devices allows the gathering of data on human mobility at an unprecedented scale and detail. This cumulative dissertation deals with several important aspects of the collection, processing and application of such data. The work presented is all in the context of the MOBIS study, a nationwide field-experiment on mobility pricing, using a smartphone-based GPS tracking app, Catch-my-Day. First, the recruitment and study design of the MOBIS experiment are presented. The meta-behaviour of the respondents in the study is analysed, identifying important factors influencing the rate of attrition in long duration tracking studies. In the second paper, a method for estimating the external costs of road transportation based on GPS data and using the MATSim framework is developed. The amount of data collected through such tracking studies is massive, presenting a challenge for the application of discrete choice methods. This is the topic of the third paper. Here, a new software package for R, called mixl, is presented. The final paper presents the initial descriptive results of the impacts of the Covid-19 pandemic on mobility behaviour in Switzerland. Here, the original MOBIS-panel was re-invited to use the tracking app. Drastic changes in travel behaviour are identified as a result of the restrictions, and the implications for future transport policy discussed. In closing, this dissertation presents a mixture of methodological and applied work centered around the use of smartphone-based GPS tracking in transportation research. The methodological contributions will help inform the design of future tracking studies and field experiments, and the insights gained into mobility behaviour during the pandemic will hopefully stimulate further research efforts