Generalized profitable tour problems for an online activity routing system
by Joseph Chow
Chow, J.Y.J., Liu, H., 2012. Generalized profitable tour problems for an online activity routing system. Transportation Research Record, accepted for publication.
A next generation online route guidance and activity recommendation system is studied for supporting decisions related... more A next generation online route guidance and activity recommendation system is studied for supporting decisions related to selecting multiple activities considering both the activity utilities with their spatial proximities and scheduling them for a user. To solve the underlying problem, extensions of the profitable tour problems and prize collecting traveling salesman problems to generalized cases—by expanding single nodes to clusters—are proposed to handle different activity types. The generalized formulations are shown to address a number of different uses including routing with refueling, the Pub Crawl Problem, and the Romantic Date Problem. Test cases are conducted to compare an insertion heuristic and a multi-solution genetic algorithm with exact solutions to provide further insight. Both algorithms work quite well even with time window constraints and considering the need for fast computational times in an online decision support environment. The multi-solution genetic algorithm tends to be slower than the insertion heuristic, but it can handle a wider variety of problems and can also provide a set of solutions from which a user can browse to account for unobserved preferences.
Inverse optimization with endogenous arrival time constraints to calibrate the household activity pattern problem
by Joseph Chow
Chow, J.Y.J., Recker, W.W., 2012. Inverse optimization with endogenous arrival time constraints to calibrate the household activity pattern problem, Transportation Research Part B 46(3), 463-479.
A parameter estimation method is proposed for calibrating the household activity pattern problem so that it can be... more A parameter estimation method is proposed for calibrating the household activity pattern problem so that it can be used as a disaggregate, activity-based analog of the traffic assignment problem for activity-based travel forecasting. Inverse optimization is proposed for estimating parameters of the household activity pattern problem such that the observed behavior is optimal, the patterns can be replicated, and the distribution of the parameters is consistent. In order to fit the model to both the sequencing of activities and the arrival times to those activities, an inverse problem is formulated as a mixed integer linear programming problem such that coefficients of the objectives are jointly estimated along with the goal arrival times to the activities. The formulation is designed to be structurally similar to the equivalent problems defined by Ahuja and Orlin and can be solved exactly with a cutting plane algorithm. The concept of a unique invariant common prior is used to regularize the estimation method, and proven to converge using the Method of Successive Averages. The inverse model is tested on sample households from the 2001 California Household Travel Survey and results indicate a significant improvement over the standard inverse problem in the literature as well as baseline prescriptive models that do not make use of sample data for calibration. Although, not unexpectedly, the estimated optimization model by itself is a relatively poor forecasting model, it may be used in determining responses of a population to spatio-temporal scenarios where revealed preference data is absent.
