Abstract:

To fill the research gap, a HVRP for hazardous materials transportation was proposed in this study, aiming at optimizing the three objectives as total risk, total cost and total carbon emissions. Firstly, in the model construction stage, the measurement methods of total cost and total risk were improved, including establishing a loading-dependent risk quantification method for explosion scenarios, and designing a specific soft time window for penalty cost calculation, which could preferentially reduce the waiting time of vehicles with large loads at customers. Then, to better solve the above model, the NSGA-II was improved in two aspects. A hybrid crossover method with new crossover operators was designed to improve the global search efficiency, and a two-stage variable neighborhood search (VNS) algorithm was adopted to improve the local search ability. Finally, a numerical example was given to verify the effectiveness of the model and algorithm. The results indicate that, compared with the original NSGA-II, the convergence curve of the improved algorithm decreases faster, and the average values of the three optimization objectives of total cost, total risk and total carbon emissions are further reduced by 3.36%, 12.16% and 6.96% respectively. In a fleet with limited number of vehicles, the carrier can have different degrees of influence on each target by choosing different vehicle types.

Key words: carbon emission, hazardous materials, heterogeneous vehicle routing problem (HVRP), multi-objective optimization, non-dominant sorting genetic algorithm II (NSGA-II)