| With the rapid development of social economic,large quantity of hazardous materials(hazmat)is used in the manufacturing industry and national life,and the transport demand of hazmat by road is increasing.The difference between the hazmat and the ordinary materials in transportation process is that the former has inherent risk characteristics.Once the leak,fire or explosion incident occurs during the transportation,it will cause serious disaster to the lives and property of residents around the accident point,and it may also cause serious pollution to the surrounding ecological environment.Therefore,the transport risk management is necessary in the process of hazmat transportation,and the existing studies have shown that transportation path optimization of hazmat could reduce the transport risk effectively.According to the existing literature,there are some deficiencies in the study of transportation path optimization for road hazmat,such as the path optimization problem for multiple types of hazmat transported jointly,the path optimization problem of road hazmat transported in a dynamic road network,and the risk distribution problem of road hazmat in transportation process and so on.For this reason,this paper combines the essential characteristics of the transportation path optimization of road hazmat with the transport needs in actual,the path optimization problem of hazmat transportation is systematically studied from the perspective of theoretical analysis and practical application to achieve multi-criteria route optimization under different transport environments and constraints.This paper comprehensively considers multiple optimization criteria of different decision makers in transportation path optimization for road hazmat,and combines the characteristics of transport networks to establish a multi-criteria optimization model under different transport conditions,and the solution algorithm is designed to generate non-dominated path set for each model to provide scientific and practical decision support for government authority and hazmat carriers.The research also provides theoretical support and technical support in the analysis of road hazmat transport network,the multi-criteria optimization methods for hazmat transportation and the distribution of transport risk in the transport network.The main contents of this paper are stated as follows:(1)The methods of risk analysis and risk measurement of road hazmat transportation are studied.The risk analysis and risk measurement can provide the decision attribute value for the minimal risk objective function of hazmat transportation path optimization problem,and also provide an evaluation index for the path optimization of road hazmat by the analytical method.(2)The multi-criterion path optimization problem of road hazmat in a static transport network is studied.A multi-criterion path optimization model is established for single-type hazmat firstly,and various pruning strategies are designed to improve the efficiency of the multi-dimensional label correcting algorithm.The combination optimization problem for multi-type of hazmat transportation paths is studied secondly,a bidirectional topology search algorithm is designed to generate k-residual transport network based on the risk characteristics of different types of hazmat and the risk thresholds on the road network,and the optimal path is searched for single criterion in the k-residual network by using the improved label correcting algorithm.According to the path selection needs of decision-makers,different paths are combined and optimized,and the adjustment strategy of critical links between paths with risk threshold on links is given.(3)The multi-criterion path optimization problem of road hazmat in a dynamic stochastic transport network is studied.The dynamic characteristics and stochastic attributes of hazmat transport network are analyzed,and the calculation method of attribute values of each link is given.The transportation path optimization problem for single type hazmat is studied firstly,the travel time and the population affected around each link are curve-fitted in piecewise continuous time interval.The mathematical model is constructed by taking the arrival time window as constraint condition and the stochastic attribute value of travel time and transport risk as optimization criteria.A two-phase multi-dimensional label correcting algorithm is designed and the non-dominated path set is generated at different departure time to meet the arrival time window with predetermined confidence level.The criteria-weight and threshold-dominate methods are proposed to achieve the balance between computational efficiency and results quality.The transportation path optimization problem for multi-type hazmat is studied secondly.The combination optimization process of multiple paths under different transportation scenarios is analyzed.With different optimization criterion,we choose single transportation path and determine the best departure time for each type hazmat,and then achieve the best combination among these paths.(4)Considering the spatial distribution characteristics of transport risk over the road network,the multi-criterion transportation path optimization problem for multi-type of hazmat is studied.The risk distribution characteristics of various types of hazmat transported in the same road networks are analyzed.A new method is proposed for calculating the dissimilarity of road hazmat transportation paths in accordance with the shortcomings of the existing calculation methods.Taking the minimum accumulated transport risk and maximum of the minimized dissimilarity between paths as optimization criteria to formulate an optimization model,and the improved NSGA-II is designed to generate the non-dominated path set for different types of hazmat with cooperative transportation.(5)The bi-level multi-criterion optimization problem of hazmat transportation path with risk distribution constraint is studied.The hierarchical decision-making relationship between the government authority and the hazmat carriers in hazmat transportation is analyzed.Considering the demands of different level decision-makers of transportation paths,a bi-level multi criterion path optimization model for multiple types of hazmat transported in the same road network is established,and a two stage solution strategy is designed to achieve the Stackelberg solution of the upper and lower level models interactively.(6)Consider the spatial and temporal dissimilarity between road hazmat transportation paths,the multi-criterion path optimization problem for multi-type of hazmat is studied.According to the location of the shared regions between the transportation paths for different types of hazmat,the time dissimilar properties between the paths is analyzed,and the physical network is transformed into space-time network,and a multi-criteria path optimization model for multi-type hazmat transportation is formulated based on space-time network.Combining the features of this model,the spatial dissimilarity path set is generated by a meta-heuristic algorithm,and the greedy search algorithm is designed to calculate the transportation sequence and the departure time of each vehicle for different types of hazmat transportation,aiming to minimize the maximum makespan of the all transport tasks under the constraint of minimum temporal dissimilarity between transportation paths.This paper thoroughly carries out the research on the multi-criteria path optimization of road hazmat transportation.The research conclusions provide theoretical support for the formulation of risk management strategies of government authority,and provide decision support for the actual transportation path selection of hazmat carriers. |
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