Title: Hybridization of Local Branching guided by Variable Neighborhood Search for
Ready-Mixed Concrete Delivery Problems

Authors: Verena Schmid (1), Karl F. Doerner (1), Richard F. Hartl (1), Juan-Jose Salazar Gonzalez (2)
(1) University of Vienna, Vienna, Austria
(2) Universidad de La Laguna, La Laguna, Tenerife,  Spain

Abstract:
Companies in the concrete industry are facing the following scheduling
problem on a daily basis: concrete produced at several plants has to be
delivered at customers' construction sites using a heterogeneous fleet of
vehicles in a timely, but cost-effective manner. The distribution of
ready-mixed concrete is a highly complex problem in logistics and
combinatorial optimization.

This paper proposes a hybrid solution procedure for dealing with this
problem. It is based on a combination of an exact algorithm and a Variable
Neighborhood Search approach (VNS).
The VNS is used to generate feasible solutions and to choose at each
iteration the variables to be fixed.
The exact method is based on a Mixed Integer Linear Programming (MILP)
formulation, which is solved (after an appropriated variable fixing phase)
by using a general-purpose MILP solver. In a sense, the approach follows a
Local Branching scheme. The hybrid metaheuristic is compared with the pure
VNS approach and the conclusion is that the new metaheuristic outperforms
the VNS if applied solely.