ACM Computing Surveys (CSUR)
Solving Vehicle Routing Problems Using Constraint Programming and Metaheuristics
Journal of Heuristics
CP '99 Proceedings of the 5th International Conference on Principles and Practice of Constraint Programming
Algorithms for Hybrid MILP/CP Models for a Class of Optimization Problems
INFORMS Journal on Computing
Integrated Methods for Optimization (International Series in Operations Research & Management Science)
Vehicle Routing Problem with Time Windows, Part II: Metaheuristics
Transportation Science
Computers and Operations Research
Lane-Exchange Mechanisms for Truckload Carrier Collaboration
Transportation Science
Designing Mechanisms for the Management of Carrier Alliances
Transportation Science
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Less-Than-Truckload (LTL) carriers generally serve geographical regions that are more localized than the inter-city line-hauls served by truckload carriers. That localization can lead to urban freight transportation routes that overlap. If trucks are traveling with less than full loads, there typically exist opportunities for carriers to collaborate over such routes. We introduce a two stage framework for LTL carrier collaboration. Our first stage involves collaboration between multiple carriers at the entrance to the city and can be formulated as a vehicle routing problem with time windows (VRPTW). We employ guided local search for solving this VRPTW. The second stage involves collaboration between carriers at transshipment facilities while executing their routes identified in phase one. For solving the second stage problem, we develop novel local search heuristics, one of which leverages integer programming to efficiently explore the union of neighborhoods defined by new problem-specific move operators. Our computational results indicate that integrating integer programming with local search results in at least an order of magnitude speed up in the second stage problem. We also perform sensitivity analysis to assess the benefits from collaboration. Our results indicate that distance savings of 7---15 % can be achieved by collaborating at the entrance to the city. Carriers involved in intra-city collaboration can further save 3---15 % in total distance traveled, and also reduce their overall route times.