Understanding variability in individual behaviour is crucial for the comprehension of travel patterns and for the development and evaluation of planning policies. In the last 30 years a vast body of research has approached the issue in a variety of ways, but there are no studies on the intrinsic variability in the individual preferences for mode choices in absence of external changes (or shocks) in the transportation infrastructures (i.e. introduction of new modes or major reorganization of the transportation system). This requires using continuous panel data. Few papers have studied mode choice with continuous panel data but mainly focused on the panel correlation. In this work the authors use a six-week travel diary survey to study the intrinsic variability in the individual preferences for mode choices, the effect of long period plans and habitual behaviour in the daily mode choices. Mixed logit models are estimated that account for the above effects as well as for systematic and random heterogeneity over individual preferences and responses. The authors also account for correlation over several time periods. The results suggest that individual tastes for time and cost are fairly stable but there is a significant systematic and random heterogeneity around these mean values and in the preferences for the different alternatives. The authors found that there is a strong inertia effect in mode choice that increases with (or is reinforced by) the number of times the same tour is repeated. The sequence of mode choice made is influenced by the duration of the activity and the weekly structure of the activities. Finally, models improve significantly when panel correlation is accounted for. But it seems that inertia can explain to some extent for panel effect.
Transportation, 2014, Vol 41, Issue 6, p. 1245-1262