Tracing the planning and execution of activities and their attributes - Design and application of a hand-held scheduling process survey

The development of traffic simulation models has matured considerably in the last few decades to the point where traffic flow simulations in urban areas or on highways have become visually and behaviorally rich. Using such models to accurately forecast the impacts of emerging travel demand management policies and intelligent transportation systems has met with considerable challenge. This is because such policies do not have a consistent or simple impact on a particular groups or particular type of trips generated from a zone in a single time period. Rather, such policies effect people at a very individual level invoking changes in the nature of the activities that they and the way they are subsequently planned and executed over multiple time periods and space. This process of change or activity scheduling decision process underlies the generation of trips over time and space. The ability to develop new models of trip generation that replicate and/forecast time dependent O-D matrixes would appear to benefit from a closer examination of underlying decision processes. In particular, the sequence of decision making involved in the scheduling process (included decisions concerning what activities to perform, when, where, and by what mode), and that attributes of activities that effect these decisions (their spatial, temporal and interpersonal fixity/flexibility), need to be investigated. This paper describes a new approach to tracing these underlying activity scheduling decision processes. The goal was to utilize a computerized hand-held survey instrument that allows the gathering of information from subjects as close in time to real decision points. The computerized platform also enables the instrument to automatically trace and/or prompt for certain attributes of the decisions process, such as the sequence of decision inputs, thereby reducing respondent burden. The complete survey includes a pre-interview, exploration of an individual’s activity-repertoire, an initial data-entry, a multi-day main scheduling exercise, and a post-interview, all implemented on a computerized handheld personal digital assistant (PDA). During the scheduling exercise, subjects are instructed to continue adding activities they have planned for future days, but also to make modifications/deletions to activities as they change, and update undecided or partially planned activity attributes. They are instructed to do so whenever a decision about one or more activity-attributes or activities as a whole occurs. All the while, the program automatically tracks the sequence of decisions made, and prompts the user for supplemental information on certain decisions, such as the reasons for the modifications, or when exactly that particular decisions may have been made (this is especially important for tracking impulsive decisions that are entered into the program “after-the-fact”). A pretest conducted in September 2002 and the main survey of 400 individuals in November 2002 to February 2003 demonstrated very good results in terms of user handling and understanding, software functionality and data quality.