The transport implications of activity and time budget constraints

Time budget and activity analysis ideas from sociological and geographical disciplines are reviewed in a transport context. A systematic examination of international data sources shows a regular structure, which applies only at a fairly aggregated level. The modelling structures so far used include stochastic models and entropy maximisation approaches: both appear to be able to replicate certain aspects of the linkage between and the duration spent in different activities, although from contradictory bases. The competition for travel time is shown as a function of stafe in family life cycle, with the pressure on trip combination, destination substitution, and on other activities such as sleep and leisure. The different forms of time expenditures at different locations are related to different appraisal purposes, including environmental exposure. Data from over 14 countries including Australia show broadly similar trends in travel time budgets, but little advance has yet been made in proving an effective model of the elasticity and cross-elasticity of demands for time for different activities. Moreover, the variations in personal budgets which show up at almost any level of disaggregation suggest that analysis by market segments will be essential. The first order variations in travel time budgets, income, and vehicle licence holding, and detailed analyses of household interview data should first be carried out to establish the links between time and financial budgets in satisfying the activity programs which transport sustains. The implications of an activity program approach for the valuation of time savings are considered.