Carbon trading policy, as an important¹ approach to energy conservation and emission reduction, is being applied by an increasing number of cities at home and abroad with a certain effect. Meanwhile, traffic is a major source of energy consumption and carbon emission in cities and thus a main field of energy conservation and carbon emission and a carbon emission trading object in cities. Globally, the carbon trading policy is rarely adopted in the traffic sector. Emission monitoring and quota allocation are challenging tasks due to several characteristics, such as the mobility and dispersibility of vehicles and non-profitability of certain sectors. Therefore, the inclusion of the transportation sector in the carbon emission trading policy framework remains an issue. On the basis of the definition of the carbon emission trading policy framework, this study draws certain elements of applicability of carbon emission trading policy and conducts an empirical analysis of the applicability of the participation of the transportation sector in carbon emission trading.

The adjustment of transport structure is a major decision made by the CPC(Communist Party of China) Central Committee with General Secretary Xi Jinping as the core. This decision is an important link to reduce air pollution and achieve environmental protection. Promoting the "road to railways" for cargo transportation, reducing the amount of road freight, and increasing the amount of railway freight transportation are vital for preventing and controlling air pollution in the Beijing-Tianjin-Hebei region and accelerating the construction of a modernized and integrated transportation system. On the basis of the analysis of the status quo of freight transportation in the Beijing-Tianjin-Hebei region, this article presents an understanding of the structure adjustment of such freight transportation and proposes optimization strategies.