Truck Scheduling for Waste Collection in Porto Alegre

This paper considers a truck scheduling problem in the context of solid waste collection in Porto Alegre, Brazil. The problem consists of designing ``good" daily truck schedules over a set of previously defined collection trips, on which the trucks collect the solid waste in fixed routes and empty the loads in one of the several operational recycling facilities in the system. The main objective is to minimize the total costs involved, including traveled distance and fixed truck costs, as well as to obtain balanced assignments of solid waste into the recycling facilities, due to the social benefit of the solid waste program. We model this problem as a vehicle scheduling problem (VSP) with a special structure, and employ a variation of the auction algorithm to solve it. A dynamic penalty method is embedded into the auction algorithm to achieve balanced assignments of collection trips to recycling facilities. Finally, computational experiments are conducted on real data. The results show that our approach simultaneously reduces total costs and balances the solid waste assignments to recycling facilities.