| Dangerouse materials have a broad application prospect in the national economy and play a role in promoting economic development,but at the same time the dangers it brings are increasing day by day.The optimization of dangerouse materials transportation is of great significance to reduce transportation risks,improve efficiency and promote the development of transportation industry.In this paper,with the objective of achieving the lowest risk of dangerouse materials road transportation and the main consideration of reducing the number of people affected,we conduct an in-depth analysis and research on the optimization of dangerouse materials transportation routes.The corresponding mathematical model is constructed,and the Lagrangian relaxation solution method is designed for the characteristics of the established model.Finally,the effectiveness of the proposed method is verified by analyzing the arithmetic cases,and the main contents of the paper are shown as follows:(1)Analyze the current situation of research on the optimization of dangerouse materials road transport routes at home and abroad and analyze and measure the risk of dangerouse materials road transport.We analyze the current situation of dangerouse materials transportation route optimization from three aspects: dangerouse materials transportation risk measurement,vehicle route optimization and vehicle route solution.The risk of dangerouse materials road transport is analyzed from two aspects: accident probability and accident consequence,and the risk measurement model of dangerouse materials road transport is constructed by taking the number of population exposure as the measure of accident consequence.(2)Optimization of dangerouse materials transportation path under static environment.To achieve the lowest risk of dangerouse materials road transport as the goal,and add the section risk threshold,vehicle path risk threshold and the longest time period and other constraints to establish a dangerouse materials road transport path optimization model under static environment.According to the characteristics of the model,a Lagrangian relaxation algorithm is designed to relax the coupling constraints in the model into the objective function to obtain a relaxation model,which reduces the difficulty of solving,and then decomposes the relaxation problem into multiple constrained shortest-circuit problems that are easy to solve,and designs the scalar algorithm to solve.A subgradient algorithm is used to solve the Lagrangian dual problem,which is used to obtain the lower bound of the original problem.A heuristic algorithm is designed for the feasibility of the solution to obtain the upper bound.Then the validity of the model and algorithm is verified by arithmetic examples with different size road networks and different number of vehicles.(3)Optimization of dangerouse materials transportation path in time-varying environment.In the process of dangerouse materials transportation,the population and traffic density on both sides of the same road section will be different in different time periods,so the transportation risk will be different with the change of time.Considering that the time factor has an important influence on the selection of the optimal path of dangerouse materials transportation,a spatio-temporal network model is established by introducing a time axis and constructing a spatio-temporal network to optimize the path of dangerouse materials road transportation in a time-varying environment,which is solved by using Lagrangian relaxation algorithm.Then the validity of the model and the algorithm is verified by the calculation cases with different scale road networks and different number of vehicles. |
