# Research on Freight Transportation Carbon Emission Reduction Based on System Dynamics
## 1 Introduction  
The International Energy Agency (IEA) report shows that 23% of global carbon dioxide emissions come from the transportation industry, only under the electricity and thermal energy industry (Figure 1) [1]. In the carbon dioxide emissions generated by transportation activities, the carbon dioxide generated by the transportation carrier occupies a major share in the transportation process. At present, the main cargo transportation methods are road transportation, railway transportation, water transportation, and air transportation. While road transportation and railway transportation have a large volume, the service objects of the two transportation methods have a large overlap and increase with the transportation distance. The increase in carbon emissions per unit of road transportation is higher than that of rail transportation. Therefore, this could be considered through policies, investment, and other methods to guide the transfer of conditional parts of road freight transportation to railway freight transportation. At present, energy conservation and reducing carbon emissions are hot topics on a global scale, and many scholars and institutions conduct research on these topics. Scholars have done a lot of work, such as explore the relationship between economic growth, carbon dioxide emissions, and energy consumption [2]. Some use a delayed payment strategy to reduce carbon emissions from supply chains [3]. Others do research to find if environmental innovation is useful for reducing carbon emissions [4, 5]. The impacts of human capital on carbon emissions have also been identified [6]. Government and corporate policy guidance can also effectively reduce carbon emissions [7]. The optimization of transportation infrastructure can also have an effect on the reduction of carbonemissions [8], and through effective energy management, carbon emissions can be controlled [9]. Combining multi-layer logarithmic mean Divisia index (LMDI) decomposition with hierarchical clustering has been used in emission reduction strategies [10]. Through systematic research on the consumption of renewable energy in developing countries, scholars have found ways to reduce carbon emissions [11] and conduct research on the regionality of carbon emissions through regional economic theory [12]. A simultaneous equation model and extended stochastic impacts by regression on population, affluence, and technology (STIRPAT) model based on the I = P*A*T equation (IPAT) identity were applied and achieved positive results [13; 14], and non-linear gray multi-variable models also have been considered [15]. At the same time, multi-angle research on urban carbon emissions has also been carried out [16]. The research of accounting for carbon emissions in the context of industrial transfer shows the industry impact [17]. Some scholars intend to innovate and improve materials in order to reduce carbon emissions [18]. On the other hand, others consider expanding trade openness and introducing external investment to solve the carbon emission problem [19; 20]. Many scholars are using the autoregressive distributed lag (ARDL) cointegration, Granger causality analysis, and dynamic causality analysis to research carbon emissions [21; 22]. Various industries also conduct research to reduce carbon emissions, such as cement production [23; 24]. Some scholars are also concerned about the clean energy and sustainable development of the transportation industry [25]. This paper uses the method of system dynamics, and there have been many studies on this method in recent years. Some scholars have conducted in-depth discussions and research on transportation issues using the integrated methods of system dynamics and the analytic network process (ANP) [26; 27]. System dynamics has also been applied to the sustainability research of urban development in recent years [28]. The development analysis of the digital platform also uses the method of system dynamics [29].