The Multiple Vehicle TSP with Time Windows and Equity Constraints over a Multiple Day Horizon

This paper considers the multiple vehicle traveling salesman problem cast over a multiple day routing scenario, with time windows and equity constraints. It develops an optimal column generation procedure and heuristic variations which solve test problems derived from the overnight delivery business. Extensive empirical testing indicates the judicious chose of a few routes for each day can incorporate equity at little or no additional cost.Federal ExpressNaval Postgraduate School Research Initiation ProgramNational Science Foundation- grant SES-88-10917Federal ExpressNaval Postgraduate School Research Initiation ProgramNational Science Foundation- grant SES-88-1091

Heuristics for Routing Heterogeneous Unmanned Vehicles with Fuel Constraints

This paper addresses a multiple depot, multiple unmanned vehicle routing problem with fuel constraints. The objective of the problem is to find a tour for each vehicle such that all the specified targets are visited at least once by some vehicle, the tours satisfy the fuel constraints, and the total travel cost of the vehicles is a minimum. We consider a scenario where the vehicles are allowed to refuel by visiting any of the depots or fuel stations. This is a difficult optimization problem that involves partitioning the targets among the vehicles and finding a feasible tour for each vehicle. The focus of this paper is on developing fast variable neighborhood descent (VND) and variable neighborhood search (VNS) heuristics for finding good feasible solutions for large instances of the vehicle routing problem. Simulation results are presented to corroborate the performance of the proposed heuristics on a set of 23 large instances obtained from a standard library. These results show that the proposed VND heuristic, on an average, performed better than the proposed VNS heuristic for the tested instances

Multiple Vehicle Routing Problem with Fuel Constraints

In this paper, a Multiple Vehicle Routing Problem with Fuel Constraints (MVRPFC) is considered. This problem consists of a field of targets to be visited, and a collection of vehicles with fuel tanks that may visit the targets. Consideration of this problem is mainly in the improvement of feasible solutions, but the following steps are discussed: Cost Matrix Transformation, Field Partitioning, Tour Generation and Rerouting, and Tour Improvement. Four neighborhoods were investigated (2-opt, 3-opt, Target Vehicle Exchange, Depot Exchange), using the Variable Neighborhood Descent and Variable Neighborhood Search schemes, with APD and Voronoi partition methods. These neighborhoods were compared to investigate their performance for various instances using the above schemes and partition methods. In general, 2-opt performed as well as 3-opt in less time than 3-opt; in fact, 3-opt was the slowest of the four neighborhoods. Additionally, the Variable Neighborhood Descent scheme was found to produce better results than the Variable Neighborhood Search

Arbeitsbericht Nr. 2006-05, November 2006

Ilmenauer Beiträge zur Wirtschaftsinformatik Nr. 2006-05 / Technische Universität Ilmenau, Fakultät für Wirtschaftswissenschaften, Institut für Wirtschaftsinformatik, ISSN 1861-9223 ISBN 3-938940-06-