How Do Transportation Influencing Factors Affect Air Pollutants from Vehicles in China? Evidence from Threshold Effect

In recent years, China has promoted a series of legal norms to reduce the environmental impact air pollutants from vehicles. The three main vehicle emission species (carbon monoxide, hydrocarbons, nitrogen oxides) contribute significantly pollution. this study, factor method was used estimate vehicles in 31 provinces 2006 2016. results show trend total carbon monoxide (CO) and hydrocarbons (HC) emissions decreasing with time; oxides (NOx) is divided into two stages: an upward between 2012 downward after 2012. Based on panel threshold, regression divide NOx CO four zones: low emissions, medium high extra-high emissions. Vehicle HC were zones, which corresponded Overall, pollution efficiency per capita GDP have significant inhibitory effect (NOx, HC, CO). Both passenger freight turnover roles promoting Road density road carrying capacity role Increasing truck proportion inhibits promotes urbanization rate positive Moreover, there obvious heterogeneity different zones