Vehicle routing problem
The vehicle routing problem (VRP) is a combinatorial optimization and integer programming problem seeking to service a number of customers with a fleet of vehicles. Proposed by Dantzig and Ramser in 1959, VRP is an important problem in the fields of transportation, distribution and logistics. Often the context is that of delivering goods located at a central depot to customers who have placed orders for such goods. Implicit is the goal of minimizing the cost of distributing the goods. Many methods have been developed for searching for good solutions to the problem, but for all but the smallest problems, finding global minimum for the cost function is computationally complex.
Several variations and specializations of the vehicle routing problem exist:
- Vehicle Routing Problem with Pickup and Delivery (VRPPD): A number of goods need to be moved from certain pickup locations to other delivery locations. The goal is to find optimal routes for a fleet of vehicles to visit the pickup and drop-off locations.
- Vehicle Routing Problem with LIFO: Similar to the VRPPD, except an additional restriction is placed on the loading of the vehicles: at any delivery location, the item being delivered must be the item most recently picked up. This scheme reduces the loading and unloading times at delivery locations because there is no need to temporarily unload items other than the ones that should be dropped off.
- Vehicle Routing Problem with Time Windows (VRPTW): The delivery locations have time windows within which the deliveries (or visits) must be made.
- Capacitated Vehicle Routing Problem (with or without Time Windows): CVRP or CVRPTW. The vehicles have limited carrying capacity of the goods that must be delivered.
- Vehicle Routing Problem with Multiple Trips (VRPMT): The vehicles can do more than one route.
Several software vendors have built software products to solve the various VRP problems. Numerous articles are available for more detail on their research and results.
- Dantzig, George Bernard; Ramser, John Hubert (October 1959). "The Truck Dispatching Problem". Management Science 6 (1): 80–91.
- Beck, J.C.; Prosser, P.; Selensky, E. (2003). "Vehicle routing and job shop scheduling: What’s the difference". Proceedings of the 13th International Conference on Artificial Intelligence Planning and Scheduling.
- Oliveira, H.C.B.de; Vasconcelos, G.C. (2008). "A hybrid search method for the vehicle routing problem with time windows". Annals of Operations Research. Retrieved 2009-01-29.
- Frazzoli, E.; Bullo, F. (2004). "Decentralized algorithms for vehicle routing in a stochastic time-varying environment". Decision and Control, 2004. CDC. 43rd IEEE Conference on 4.
- Psaraftis, H.N. (1988). "Dynamic vehicle routing problems". Vehicle Routing: Methods and Studies 16: 223–248.
- Bertsimas, D.J.; Van Ryzin, G. (1991). "A Stochastic and Dynamic Vehicle Routing Problem in the Euclidean Plane". Operations Research 39 (4): 601–615. doi:10.1287/opre.39.4.601. JSTOR 171167.
- Toth, P.; Vigo, D. (2001). The Vehicle Routing Problem. Philadelphia: Siam. ISBN 0-89871-579-2.