Winter gritting in the Province of Antwerp: A combined location and routing problem

The problem of winter gritting, which involves salt spreading to ensure the safety of road users, is described in detail for the Province of Antwerp. Other than location of main depots, at which all salt spreading tours originate and terminate, the problem also includes location decisions with respect to supplementary depots. Existence of supplementary depots allows trucks to refill during a tour, and thus enables tours to have double-capacity. Location decisions and the subsequent routings are further constrained by partition into districts, and by priorities associated with the roads of the network. In this paper a two-stage framework for analysis is suggested. It bonds location of main depots with routings on high-priority roads at the first stage, and location of supplementary depots with routings, which can include double-capacity tours, at the second stage. A small example demonstrates the potential savings involved in implementing the new approach.