Integrated Optimization Of The Transfer Of Freight Flow From Highway To Railway And The Transportation Flow Assignment Under Low Carbon Emissions

With the rapid development of global economy, the energy consumption rates of various industries are gradually speeding up. At the same time, the consumption of fossil energy generates large amounts of greenhouse gases, thus leading to more serious air pollution and more frequent smog phenomenon, which threatens the living condition of human. Confronted with the increase of greenhouse gases, various countries have reached a consensus to reduce carbon emissions and develop green economy. As an industry of huge energy consumption, transportation industry is the current major source of energy consumption and carbon emissions and has already become the important field to reduce greenhouse emission and slow down the deterioration rate of atmosphere. It is urgent to carry out researches in energy conservation and emission reduction and propose reasonable and effective approaches for transportation industry. Highway transport and railway transportation are two main land transportation means, which occupy a big share of cargo transportation, effectively ensuring the rapid development of state economy. As railway transportation has advantages in energy consumption and transportation cost, it is an important approach to attract freight flows from highway to railway to reduce carbon emissions, which imposes positive effect on realizing green transport.At present, researches about transferring freight flows from highway to railway is far from enough, and most of which are qualitative analysis with little systematic and scientific quantitative research. On the basis of some relative research findings, this paper takes a close look into the characteristics of our country’s highway transport and railway transportation, and focus on quantitative analysis based on optimization theory and takes qualitative analysis as complementary research method. This paper, in the context of green transport, researches and studies some relevant issues about freight flow transfer and distribution between highway network and railway network in depth and proposes new research ideas and methods for the development and construction of green transport, which is of great importance. The main research contents of this paper are as follows:Firstly, we analyze the current transportation situation and change law based on some statistical data, mainly focusing on mileage, volume of freight transportation, rotation volume of goods transport and transportation energy consumption. Meanwhile, we estimate the carbon emission intensity of highway transport and railway transportation by energy conversion method, which provides reliable reference for the value of some parameters in the following parts. It can be concluded from the analysis that the volume of freight transportation and turnover of highway transport and railway transportation have a tendency of growth and take up a high proportion in the total volume of cargo delivery and turnover. In addition, highway transport consumes huge fossil energy and emits a large amount of carbon dioxide. For a same task, the volume of energy consumption and carbon emission of highway transport is eight times higher than that of railway transportation. Thus, transferring some highway freight flows to railway can not only save a lot of energy but also significantly reduce carbon emissions, which is correspond to the development trend of low carbon transport.Secondly, we build an optimization model of path choosing and mode determination for highway-railway combined transport in the context of green transport. This model takes carbon emission cost demarcated by carbon tax into consideration and adds some constraints such as time limit, freight flow balance and carbon emission limit. Furthermore, we give a numerical example and solve it by Lingo 11.0. Although the research of this part just aims at one shipment between two fixed nodes, which may not solve the issues of optimizing freight flow transfer and distribution, it enlightens the following main research of this paper, including attributes expanding technology for freight nodes and constraints for building models.Thirdly, we also build an optimization model for freight flow transfer between highway network and railway network in the context of low carbon transport. In this model, carbon emission cost is reflected through carbon tax, and the optimization goal is minimizing the transport cost of land transport system, the transfer cost inside nodes and the carbon emission cost in the two pre-mentioned process. And the constraints comprise of the limit on the total volume of carbon emission of land transport system, one allowance of transfer for one single freight flow at most, the restraint of capacity for highway arc and railway arc, the internal transfer capacity limit of nodes and delivery time limit. This model contains 0-1 variables representing flow transfer decision and nodes choosing, which directly reflects the plan of freight flow transfer.Fourthly, we propose three heuristic algorithms (including Tabu Search Algorithm, Adaptive Genetic Algorithm and Dynamic Adjustment Particle Swarm Optimization Algorithm) to solve the optimization model of freight flow transfer between highway network and railway network in the background of green transport. Furthermore, we study and reveal the coding methods, iteration strategies and processes of these three algorithms in detail. In addition, we compare the efficiency of these three algorithms by a numerical example. It can be concluded from the result that the efficiency of the Dynamic Adjustment Particle Swarm Optimization Algorithm is the best. Because this algorithm not only takes the competition of individuals into consideration, but also considers the information sharing mechanism, which ensures the high quality of outcome compared with other two algorithms. The transfer plan is reasonable.Lastly, we set up a comprehensive optimization model of freight flow transfer and distribution between highway network and railway network in the background of low carbon transport and we give a numerical example. In fact, the transfer and distribution of freight flows are interacted with each other. Firstly, the transfer of freight flows will exert a great influence on freight flow structure and we need to redistribute freight flows on the railway network. Secondly, the redistribution of freight flows may ease the pressure of some railway segments and be helpful to further attract highway freight flows. It will influence the transfer plan of highway freight flows. Given this situation, we have to comprehensively optimize the freight flow transfer and distribution and build corresponding model based on the characteristics of railway freight flows, namely one flow couldn’t be split and paths of flows have a tree shape. We choose the relatively efficient Dynamic Adjustment Particle Optimization Algorithm to solve the comprehensive optimization model (based on tree shape path principle) for freight flow transfer and distribution between highway network and railway network.Compared with the plan without transfer, the optimized scheme leads to a dramatic reduction in the total volume of carbon emission and transport cost which contains carbon emission cost, owing to the huge cost advantage of railway transportation. The research contents of this paper play an important role in reducing carbon emissions of transportation and accords with the development trend of low carbon economy in the future.