۱- Introduction

۲- Literature review

۳- Methods and data

۴- Results and discussion

۵- Conclusions and implications

References

Abstract

With the rapid development of rail transit, a vast amount of electric power is consumed each year. However, the generation of electricity, and especially coal power generation, is an important source of greenhouse gases. Therefore, it is very important to analyze the potential of carbon emission reduction of urban rail transit based on specific electricity consumption structures. In this study, 18 cities in China were taken as the research object, and backward analysis was used to analyze the proportion limit of coal power consumption for rail transit in each city under three scenarios from 2015 to 2017. By comparing the limit value with the actual coal power consumed by urban rail transit, we analyzed the potential carbon emission reduction of rail transit relative to other traffic modes. The study results supported several conclusions. First, the traffic demand is in direct proportion to the carbon emission reduction potential in rail transit. Second, for cities with high coal power consumption, the development of ground bus transit is more conducive to achieving carbon reduction targets compared with rail transit. Finally, promoting the development of rail transit technology and lowering the energy consumption per capita unit travel distance are the fundamental ways to increase the emission reduction potential of rail transit. Therefore, as a modern transportation tool, rail transit is not an absolute emission reduction advantage for all cities. A city needs to analyze its own resource structure and travel demand together, set up suitable traffic modes to realize green growth and sustainable development.

Introduction

With the increasingly prominent traffic problems globally, the priority development strategy of public transport, especially rail transit, has been adopted by many countries. Rail transit has been vigorously promoted because of its characteristically large transport volume and low pollution potential. According to the China Urban Rail Transit Association, a total of 34 cities in mainland China had opened urban rail transit at the end of 2017, totaling 165 lines and total annual traffic volume of 18.5 billion passengers. The total length of operation lines reached 5033 km, 3884 km (77.2%) of which involved subways. Rail transit is an important part of an urban passenger transport system, and plays a great role in relieving urban traffic congestion. However, urban rail transit operations rely mainly on power resources; with the increase in operating rail length, energy consumption is increasing (Sun et al., 2018). According to the statistics of the China Urban Rail Transit Association, the energy consumption of rail transit in China reached 12.226 billion kWh in 2017. China predominantly generates electricity by burning coal; therefore, the large amount of electricity consumed by rail transit results in large amounts of greenhouse gases from the electricity generation process (Dong et al., 2018). Because of the development of urban rail transit and the huge increase of carbon emissions, the economic cost and the aggravation of environmental pollution have restricted green growth and sustainable development of cities in China and elsewhere (Song et al., 2018). Reducing the carbon emissions of rail transit systems has become a problem of widespread concern in recent years. Therefore, whether rail transit has more emission reduction advantages than other traffic modes is a question worthy of further examination. The carbon emissions arising from the consumption of electric energy in rail transit mainly come from coal power generation, and there are great differences in the power supply structure in various regions of China (Chen et al., 2018). The north of China is rich in mineral resources and relies heavily on coal power. By comparison, water resources in the south of China are abundant, and hydropower occupies an important position in the region’s power structure. The cleanliness (in terms of environmental emissions) of power in different regions is not the same (Pei et al., 2015). Therefore, the carbon emissions from the generation of electric power that is consumed by rail transit are also very different throughout China.