University of California Transportation Center

In this paper a model is developed and estimated empirically of the allocation of time to out-ofhome activities and travel. The model has three important characteristics. First, the allocation of time to out of home activities by individuals is the key concept in the research reported here. Since there exist interdependencies among time usages for different activities, the joint distribution of all relevant out of home activity times has to be taken into account. Consequently the model developed is multivariate.

Second, travel is a derived demand. The amount of travel is the result of the spatial activity behaviour of the individual. Of course, the exact relation between activity performance and travel demand is highly complex. The spatial dispersion and quality of activity locations and the scheduling of activities by individuals are both important elements that need to be studied in order to predict total travel demand from a given activity pattern. Here a much simpler approach is taken. It is assumed that total travel time expenditure over a certain time period (i.e. one week) for an activity is proportional to the total amount  time engaged in that activity.

The third main feature or the model is its longitudinal character. Longitudinal data have a number of advantages over cross-sectional (see e.g. Hensher, 1985; Davies and Pickles, 1985; van Wissen and Meurs, 1989). From a statistical point of view it allows the estimation of model parameters conditional on non-observed stationary characteristics and individual taste variations. From a theoretical point of view longitudinal data are necessary in order to identify and estimate dynamic processes. In this study only the statistical advantages of longitudinal data will be used.

This paper is organized as follows. In section two an overview is given of earlier related work on the allocation of time and the travel consequences. In section three the model methodology will be presented. Next, in section four, the data will be described briefly. Section five contains the empirical results of the model estimation. These results are evaluated and some conclusions are drawn in section six.