Analysis of Day-to-Day Variability in an Individual's Action Space: Exploration of 6-Week Mobidrive Travel Diary Data

Using 6-week travel diary data from Karlsruhe and Halle, Germany, this study examines the characteristics of individuals' action space. The extension of action space is represented by the second moment of the activity locations that it contains. Day-to-day variation in the second moment is examined. The results show that out-of-home activity orientation and commitment (e.g., obligatory activities on weekdays and discretionary activities on weekend days) influence the extension of action space. For workers and students on weekdays, the spread of activity locations and the distance from home to the centroid of activity locations are relatively stable from day to day. A substantial portion of the variations in their action spaces is due to unexplained differences across individuals that remain stable over time for each individual (unobserved heterogeneity). In contrast, random factors have dominant influences on nonworkers' weekday action spaces and on all individuals' weekend action spaces.