Do rail transits improve local air quality? Take Chengdu-Nanchang for example

AbstractMany cities in China have invested in the city ’s rail transit system to reduce urban air pollution and traffic congestion. Earlier studies rarely compare the effects of rail transit on urban air quality in different cities, providing little guidance to urban planners in solving traffic congestion and air quality. Due to the same opening date, we regard Chengdu Metro Line 4 and Nanchang Metro Line 1 as case studies. This paper attempts to examine the effects of the opening of rail transit on local air quality on the same opening date. Data were collected from 17 monitoring stations distributed along the chosen rail transit lines in both cities from 2015 to 2016 and analyzed using the regression discontinuity design to address the potential endogenous location of subway stations. The results show that subway opening in Nanchang has a better reduction from automobile exhaust than that in Chengdu. Specifically, carbon monoxide polluti on, one key tailpipe pollutant, experienced a 10.23% greater reduction after Nanchang Metro Line 1 opened. However, the point estimate for carbon monoxide in Chengdu is 22.42% and statistically significant at the 1% level. Nanchang Metro Line 1 does play an important role in road traffic externaliti es, but the benefit is not huge enough to change the overall air quality. On the contrary, the opening of the Chengdu Metro Line 4 is unlikely to yield improvements in air quality.
Source: Air Quality, Atmosphere and Health - Category: Environmental Health Source Type: research