Article ID: | iaor19992004 |
Country: | United States |
Volume: | 46 |
Issue: | 3 |
Start Page Number: | 355 |
End Page Number: | 367 |
Publication Date: | May 1998 |
Journal: | Operations Research |
Authors: | Bixby Robert E., Lee Eva K. |
Keywords: | vehicle routing & scheduling |
A branch-and-cut integer programming solver is developed for a class of structured 0/1 integer programs arising from a truck dispatching scheduling problem. This problem involves a special class of knapsack equality constraints. Families of facets for the polytopes associated with individual knapsack constraints are identified. In addition, a notion of ‘conflict graph’ is utilized to obtain an approximating node-packing polytope for the convex hull of all 0/1 solutions. The branch-and-cut solver generates cuts based on both the knapsack equality constraints and the approximating node-packing polytope, and incorporates these cuts into a tree-search algorithm that uses problem reformulation and linear programming-based heuristics at each node in the search tree to assist in the solution process. Numerical experiments are performed on large-scale real instances supplied by Texaco Trading & Transportation, Inc. The optimal schedules correspond to cost savings for the company and greater job satisfaction for drivers due to more balanced work schedules and income distribution.