Considering joint trips and activities in week activity schedules

People undertake trips and activities either alone or jointly with others. Including such joint actions in travel demand models increase behavioral realism, but it would also add complexity to the modeling process. To understand the importance of joint actions, it is first necessary to investigate their specific characteristics such as purposes or timing. So far, these characteristics are underrepresented in travel demand models, particularly in those dealing with simulation periods exceeding one day. Here, we introduce a method to extract joint actions from household one-week- survey data and investigate their characteristics. We show that about 20% of all trips and 18% of all activities are undertaken jointly. Moreover, we find significant differences in the proportion of joint actions for different activity types and categories of people. For example, leisure and shopping actions are more often undertaken jointly, and pensioners undertake more joint actions than employed persons or students. Because the characteristics of joint actions differ from those of actions undertaken alone, modeling these actions explicitly and integrating their characteristics into travel demand models increases behavioral realism and improves results.