A NEW BI-OBJECTIVE MODEL FOR A TWO-ECHELON CAPACITATED VEHICLE ROUTING PROBLEM FOR PERISHABLE PRODUCTS WITH THE ENVIRONMENTAL FACTOR

In multi-echelon distribution strategy freight is delivered to customers via intermediate depots. Rather than using direct shipments, this strategy is an increasingly popular one in urban logistics. This is primarily to alleviate the environmental (e.g., energy usage and congestion) and social (e.g., traffic-related air pollution, accidents and noise) consequences of logistics operations. This paper represents a two-echelon capacitated vehicle routing problem (2-ECVRP) in which customers' satisfaction and environmental issues are considered for perishable goods delivery for the first time. The paper proposes a novel bi-objective model that minimizes: 1) total customers waiting time, and 2) total travel cost. A restriction on maximum allowable carbon dioxide (CO2) emissions from transport in each route is considered as environmental issue in the problem. The proposed model is solved by simple additive weighting (SAW) method. Finally, the proposed model is applied to a real world problem in a supermarket chain. The results achieved by GAMS optimization software confirm the validity and high performance of the model in respect to the importance of the each objective function. Furthermore, the sensitivity analysis performed on the model reveals that less restrictive policies on carbon emissions lead to more total emissions but less total travel cost and customers waiting time.