Exploring Variation Properties of Departure Time Choice Behavior by Using Multilevel Analysis Approach

The variation properties of departure time choice behavior are examined by activity type with the use of a continuous 6-week travel survey collected in the cities of Karlsruhe and Halle, Germany, in 1999. The total variation in departure time choice is divided into five variation components: spatial variation, temporal variation at the aggregate level, interhousehold variation, interindividual variation, and intraindividual variation. These variations are first quantitatively analyzed by using a multilevel modeling approach without considering the influences of explanatory variables. Then, on the basis of the clarified variations patterns, how much of the variations can be captured by explanatory variables is examined. It is confirmed that different activities show quite different variations, and of the variations the intraindividual variation accounts for the largest percentage of the total variation. Model estimation results further underscore the need for simultaneously dealing with unobserved macrolevel variations, especially interindividual, interhousehold, and spatial variations, as well as the intraindividual variation, even when the explanatory variables are included in the model. Such quantitative assessment of various types of variations based on a multilevel modeling approach provides a useful guide for the specification of behavior models and deepens the knowledge of behavioral variability by going beyond the traditional paradigm, which focuses on a limited set of variations.