Key influencing factor and future scenario simulation of China's CO2 emissions from road freight transportation

Road freight transportation is a main source of carbon dioxide (CO2) emissions in the transportation sector, and different factors may affect road freight CO2 emissions. However, most studies focus on the influences of a few factors due to the high correlation between factors. Hence, this study adopts a partial least squares regression model to quantify the influences of diverse variables, including pre-treatment variables (which are hard for policy-makers to control) and post-treatment variables (which policy-makers have more control over). Before modeling, road freight CO2 emissions in China for 1999–2019 are estimated. The results show that population growth is a key reason for the increase in road freight CO2 emissions. Among the post-treatment variables, market share, diesel price, and number of freight vehicles play key roles in changes in road freight CO2 emissions. More importantly, road freight CO2 emissions per unit gross domestic product are estimated to be 4.65 g/CNY (Chinese Yuan) in the 2030 business-as-usual scenario, while there remains a 2 g/CNY gap compared to the ideal target. Even in a policy stimulus scenario, all post-treatment variables should be greatly improved to achieve the expected 2030 CO2 emission reduction target for road freight transportation. The above results emphasize the long-term and difficult nature of reducing CO2 emissions from road freight transportation.