Path analysis of factors in energy-related CO2 emissions from Beijing's transportation sector

- Path analysis model can estimate the direct and indirect effect separately.
- Path analysis model can reveal all aspects of the relationship among variables.
- Population has the greatest positive impact on CO2 emissions.
- The growth of PGDP can reduce the energy intensity and transportation intensity.
- The change of economic growth pattern inhibits the growth rate of CO2 indirectly.

The transportation sector is one of the major driving forces of carbon emissions. Identifying the factors that affect CO2 emissions from the transportation sector is important to build a low-carbon city. Most existing research focuses on the total effect of factors on CO2 emissions while the indirect influence is also the driving force of CO2 emissions. Additionally, identifying the causal relationship between variables is helpful to study the mutual acting mechanism. Therefore, this paper uses the path analysis model to estimate the direct, indirect and total influences of driving factors on transportation CO2 emissions in Beijing and investigate the causality relationships between variables. The results show that reducing energy intensity and transportation intensity are the key factors in controlling the increase of transportation-related CO2 emissions. Population has the greatest positive impact on CO2 emissions because an increasing population is leading to growth in energy consumption and the number of motor vehicles. However, population could indirectly affect the energy intensity and transportation intensity to reduce carbon emissions. Moreover, motor vehicles increase CO2 emissions due to the growth in private car population and its low energy efficiency. And, the change in the economic growth pattern somewhat inhibits the growth rate of CO2 emissions by reducing the energy intensity and transportation intensity indirectly. To further suppress the growth of transportation carbon emissions, the following steps should be taken: appropriately improve the quality of population, control the scale of motor vehicles, develop and promote clean energy, and reduce traffic energy intensity and transportation intensity.