University of California Transportation Center

Trip chaining is a phenomenon that has a significant impact on urban transportation and activity systems. This paper argues that an appropriate representation of the underlying behavioral processes in models of trip chaining is crucial to the capability and reliability of the models. To examine the behavioral processes, data on the complete processes of activity scheduling and trip chaining were collected with a computerized survey instrument, REACT!. The scheduling horizons of sojourn activities were analyzed with contingency tables. The results of this analysis indicate that some of the decision elements entailed in trip chaining were opportunistically formed within constraints set by previously planned activities. While engaged in earlier activities, individuals might see opportunities of carrying out certain activities at different locations occurring later in the day. The decisions as to whether to take these opportunities or not would depend on their evaluation of scheduling feasibility (e.g., the travel time required to reach these activities). However, the analysis also illustrates that some trip chains were indeed executed as planned, suggesting optimality and potential routine behavior. Based on the empirical evidence, transactional opportunistic planning within a constrained environment is viewed as a potential behavioral model for trip chaining behavior.