Sustainable traveling purchaser problem with speed optimization

This paper addresses a multi-objective single-product network design and operations problem that consists of selecting the suppliers, allocating the orders, routing a single vehicle to collect the purchased items, and choosing the vehicle speed levels. The objective functions minimize the purchasing and transportation costs, the fuel consumption, and consequently the CO₂ emissions, and maximize the total sustainability value of the purchased products. The proposed model is an extension to the well-studied traveling purchaser problem and pollution routing problem in the sense that it integrates the social and environmental sustainability aspects in the supplier selection process in addition to cost and CO₂ emissions. The model is solved using the branch-and-cut algorithm as well as a proposed genetic algorithm. An extensive numerical study shows that the proposed heuristic converges to the optimal solution in few minutes for the considered instances.