Research On Multimodal Transport Network Optimization Of Hazardous Material Under Time-varying Conditions

With the rapid development of China’s economy,and the rapid rise of the chemical industry,the transportation demand for hazardous material is expanding.Due to the unbalanced economic development among regions in China,most production and consumption places of hazardous material are often in different area and far away,and multimodal transport can well meet such demand.Hazardous material accidents have the characteristics of low probability and great harm once happening.Multimodal transportation involves a variety of different modes of transportation and two aspects of transporting and transferring,and the time has an influence on the risk and the cost.The network optimization including reasonably allocating network traffic and select transportation routes and modes is able to reduce transportation risks of multimodal transportation effectively and meet the demand of both the government and the carrier.Firstly,the risk analysis,network optimization and risk equity of hazardous material are reviewed in detail.It is found that there are few researches on the network optimization of multimodal transportation of hazardous material,mainly static network without considering the time-varying characteristics of risk and cost,and without describing the transshipment process in detail.The network optimization model is only made with cost and risk as the objective functions,less considering the risk equity.Therefore,this paper will make a research the multimodal transport network optimization of hazardous material under timevarying conditions.Secondly,considering the characteristics of multimodal transport and transshipment process which is subdivided,and the risks of the population,property,and environment,also the impact of time on the risk,the risk measurement model of multimodal transport of hazardous material under time-varying conditions is established on the basis of the traditional risk model.Analyzing the composition of the cost of multimodal transport of hazardous material and considering the impact of time on the cost,the cost measurement model of multimodal transportation of hazardous material under time-varying conditions is established.Then,according to the analysis of multimodal transport process of hazardous material,the risk variance is used to measure the transport and transshipment risk equity for establishment of the multimodal transport risk equity measurement model.After analyzing the multimodal transport network optimization problem of hazardous material,the model of multimodal transport network optimization problem of hazardous material under timevarying conditions is established on bi-level programming,which takes minimizing risk and maximizing risk equity as the upper layer objective functions and minimize the cost as the lower one.Finally,according to the characteristics of this model,the upper and the lower layer interactive iteration is used as the solution idea and the method of improved PSO is selected and realized by Python.From the aspects of whether the time-varying conditions,different departure time,and whether the risk fairness,the conclusions are analyzed and made.All as follows:(1)the multimodal transport plans with or without time-varying conditions is different and have different objective function values and the decisions of the government and carrier are affected by it;(2)The risks and costs of the same multimodal transport plan are different at different departure times,and the multimodal transport plans in different departure time is different,and the government and carrier can decide on their own demands due to the reduction of the risk and the cost or the balanced risk distribution caused by the reasonable departure time;the multimodal transport plans considering the risk equity passes through more transport sections and transfer points,whose risk difference is lower,and the risk distribution of network is more balanced.The multimodal transportation network optimization model of hazardous material considering risk equity under time-varying conditions is established,which can meet the requirements of the government for safety and the carrier for cost,and more in line with the actual transportation than the static network.Considering the risk equity can reduce the risk difference of the network and conducive to the overall risk control of the network,which is in certain practical significance.