The planar multifacility collection depots location problem

The multifacility collection depots problem is the location of one or more facilities among a given set of demand points and a given set of collection depots. Each service consists of a trip to the customer, collection of materials, dropping off the materials at one of the available collection depots, and returning to the facility to wait for the next call. The trip can be done in reverse, i.e., collecting the materials on the way to the customer. The objective is to minimize the total travel time. The same model can be used for locating collection depots among a given set of demand points and existing facilities. The problem is analyzed and several properties proved. A solution within a given accuracy of the optimal solution is found for the single facility problem. Heuristic solutions are proposed for locating multiple facilities. Extensive computational experiments confirm the effectiveness of the solution approaches. (C) 2018 Elsevier Ltd. All rights reserved.