Green infrastructure and air pollution: Evidence from highways connecting two megacities in China
研究了2015年连接成都和重庆的高铁开通对沿线高速公路空气污染的影响，发现一氧化碳和PM2.5分别下降6.4%和7.1%。
Following market liberalization, the vehicle population in China has increased dramatically over the past few decades. This paper examines the causal impact of the opening of a heavily used high speed rail line connecting two megacities in China in 2015, Chengdu and Chongqing, on air pollution. We use high-frequency and high spatial resolution data to track pollution along major highways linking the two cities. Our approach involves the use of a novel augmented regression discontinuity in time approach that incorporates machine learning to inform our specification choice in the first stage. Our estimates show that CO is reduced by 6.4% and PM2.5 by 7.1% along the main affected highway. These findings are supported using a difference-in-differences approach.