INFLUENCING MECHANISM OF METRO LINES ON AIR QUALITY AND PLANNING STRATEGY:AN EMPIRICAL STUDY BASED ON THREE METRO LINES IN WUHAN
Megacities in China have vigorously promoted the construction of urban rail transit in order to alleviate urban traffic congestion and improve the air quality.However,there is still a lack of empirical research on whether the metro can substantially improve the air quality along the line.Taking Wuhan Metro as an example,this paper uses the difference-in-difference method to evaluate the impact of the metro on air quality,analyzes the mechanism,and proposes the planning strategy.The results show that the influence of metro on the air quality is spatially heterogeneous along the line,in which the configuration and spatial layout of the built environment along the line are the key influencing factors.In low-density urban areas,the traffic substitution effect is greater than the traffic creation effect,which helps to improve the air quality.While in the high-density area,the traffic creation effect is greater than the traffic substitution effect,which aggravates the air pollution.Therefore,the construction of metro projects in megacities should be organically combined with urban land use and spatial planning,and the differentiated development mode should be adopted based on the urban density along the metro line.It is advisable to reduce the population density in the downtown area,instead of pursuing high-density development unilaterally along the line.
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