Four basic hypotheses about activities that are fundamental to pursuing an activity-based travel-forecasting modeling procedure are presented. They include classifying activities as mandatory, flexible, or optional; using life-cycle stages to differentiate the amount of time spent on different activities; determining whether there are differences in proportionate amounts of time spent on activities by gender; and examining role allocations to activities between people in a household on the basis of working status and gender. The hypotheses are tested by using a subsample of households from a sample collected in Boston in 1991 from an activity diary. Within the limitations of the data, it is found that the classification of activities appears to be sensible, and statistically significant differences are found among life-cycle groups. Differences are also found by gender and working status. Recommendations are made for further research and on some of the implications of these findings for activity modeling.
Mechanisms of Modificational Variability