Expansion of city scale, traffic modes, traffic congestion, and air pollution

Abstract

In recent years, the number of large cities and the incidence of urban haze have been increasing. However, whether population growth inevitably leads to air pollution is controversial. The expansion of city scale is accompanied by changes in traffic mode and traffic congestion. However, whether such expansion influences traffic and wields a significant impact on air pollution remains unknown. Thus, this research attempts to clarify the influence mechanism of city-scale expansion on air pollution and analyze the expansion of city scale, traffic, and air pollution in the same framework. First, we find that city-scale expansion can directly influence air pollution. The scale effect of energy consumption caused by such expansion significantly aggravates air pollution, whereas the structural and technological effects can effectively improve air quality. Second, green mode of transportation can reduce air pollution, whereas traffic congestion worsens air pollution by increasing the commuting time. Third, we find that the city-scale expansion can both alleviate and worsen air pollution by promoting public transport and exacerbating traffic congestion, respectively. Therefore, the effect of city-scale expansion on air quality by influencing traffic is clearly a “double-edged sword.”