14: Multi-Day and Multi-Period Data

For infrastructure planning, data collection used to be orientated to traffic modelling and focused on peak hours for an “average” spring or fall weekday (holiday periods excluded) i.e., when the volume of traffic is highest. Nowadays, the main interest is shifting from designing infrastructure to enhancing communities and the environment, leading to a change in data needs away from the most detailed description of traffic (O-D matrices, etc.), to a better understanding of individual behaviour, not only during a single day but over the entire year. Indeed, the flexibility and constraints (for travel needs, modal shift, etc.) can only be detected from a long enough temporal perspective. Moreover, it can be argued that a solution to environmental issues lies in changing travel behaviour towards a more sustainable form of mobility. However, standard, one day, trip based surveys give a poor description of these changes and barely allow one to distinguish real changes in travel behaviour from changes caused by specific trends in their explanatory factors (for instance, low growth rate and high unemployment in Continental Europe during most of the 1990s).