Exploring the effect of urban traffic development on PM_2.5 pollution in emerging economies: fresh evidence from China

Urban traffic congestion and haze pollution have become the main obstacles to the development of most cities in emerging economies. It is not clear how urban traffic development processes impact on PM_2.5 concentration for the cities of emerging economies. Motivated by exploring the relationship between urban traffic development and PM_2.5 pollution, 30 provinces in China (a representative emerging economy) from 2007 to 2016 were taken as examples, and threshold regression model and geographically temporally weighted regression model were used to explore the nonlinear relationship and their spatio-temporal heterogeneity. These empirical researches demonstrated that the impact of urban traffic development on PM_2.5 pollution has a significant threshold effect. That is, when the road area crosses the threshold, it will significantly aggravate the regional PM_2.5 pollution. Meanwhile, regional economic development also shows a significant threshold effect. Moreover, the relationship between urban traffic development and PM_2.5 pollution in various Chinese provinces presents significant spatial heterogeneity. Specifically, the Chinese provinces are divided into four categories, and urban planning should be designed for different types for the sustainable development of the economy and environment. Our results not only contribute to advancing the existing literature, but also merit particular attention from urban planners in emerging economies.