State-of-the-art of longitudinal travel surveys: a comparison of the MOP and MPN

Longitudinal travel surveys are needed to measure and study changes in individual travel behaviour. Due to the complexity of setting up and managing a longitudinal travel survey, only a limited number of such studies investigating travel behaviour at the national level have existed. The Netherlands Mobility Panel (MPN), which started in 2013, is currently the only active longitudinal travel survey at the national level. Until 2023, besides the MPN, the German Mobility Panel (MOP) was also active. The MOP existed since 1994, but ceased at the end of 2023, after almost 30 years. 

Together with the Karlsruhe Institute of Technology (KIT), the operators of the MOP, the Netherlands Institute for Transport Policy Analysis (KiM) listed the differences and similarities between the MPN and MOP. We also investigated how design choices when setting up a longitudinal travel study can affect the outcomes. We do this by assessing representativeness, diary fatigue (this refers to the extent to which respondents report fewer trips as the diary period progresses) and dropout of respondents from the panel. This study thus provides insight into important aspects to consider when designing a new and maintaining an existing longitudinal travel survey.