Green vehicle routing problem with simultaneous pickup delivery, time windows, stochastic demand and varying travel time: A case study of suntory pepsico Vietnam beverage

Abstract

Suntory PepsiCo Vietnam Beverage (SPVB) is the top famous supplier in the F&B industry in Vietnam. Because of the intense competition, there is a high priority in improving the company’s transportation systems. Nevertheless, SPVB truck fleet planning currently does not take into account the variation of travel time during the day. The company’s pickup demands of empty bottles are also unknown until trucks arrive at destinations, resulting in uncollected demand. More importantly, to achieve sustainable development, environmental factor should no longer be ignored. As a result, an efficient route should contain both economic and ecological aspects. This study attempts to solve the green vehicle routing problem with simultaneously pickup – delivery, time windows, stochastic demand and varying travel time. A mixed integer nonlinear programming model with minimum total costs and environmental impact is applied, and exact solution is obtained using CPLEX. In addition, a stochastic approach is implemented to account for uncertainty in pickup demand. This study also applies heuristic solution method, with a hybrid of Genetic Algorithm, GRASP, Tabu Search, and Ant Colony Optimization algorithm. A set of benchmark instances was used to evaluate the efficiency of the two mentioned methods. The results indicated that the hybrid method achieved near-optimal objective function values, with an average gap of 0.82% from the best known solution. The computational time of the hybrid algorithm for the 65-node instance is 8.110 seconds, much lower comparing to the computational time of 13.418 seconds for the 10-node instance by CPLEX. The percentage of pickup demand collected is 81%. This is a significant improvement, since currently only approximately half of the demand is collected. In conclusion, the heuristic method with much lower computational iii time and small gap from the best known solution is a practical option for SPVB and other companies with transportation network having similar characteristics. Keywords: vehicle routing problem (VRP); time window delivery; simultaneous pickup and delivery; green logistics; varying travel time.