Abstract: Because there are lots of sources of air pollution, it is difficult to define and distinguish pollution sources in general. For example, whether traffic jams aggravate the deterioration of air quality isnotclear. In this paper, a special instrumental variable is used to solve this problem. The peak hours of Beijing working day, cars are prohibited by the tail number., which provides some more rigorous evidence. Since Beijing carried out driving-restriction-policy, there has been an end-number-four phenomenon: whenever end number four of license plate is restricted, traffic congestion arises. This Chinese-culture-driven-phenomenon provides a novel approach to identifying traffic congestion. We collect hourly PM2.5 data from 35 monitoring stations and exploit difference-in-difference method to filter out potential contamination. The results show weekdays restricting end-number-four experience relatively 9.46%more increase from non-traffic-busy to traffic-busy hours. Traffic congestion has significantly reduced the quality of air.

Key words: air pollution, traffic congestion, air quality, difference in difference JEL Classification: Q53, Q58, R41

摘要： 由于空气的污染来源众多,交通拥堵是否加剧了空气质量的恶化,一般情况下很难界定和区分。本文利用一个特殊的工具变量——北京市工作日高峰时段汽车根据尾号限行,来分析和回答上述问题。由于受文化习惯影响,居民在挑选车牌号码时一般都不选4,因此包含数字4的车牌号很少。每当限行尾号为4和9的工作日,北京市的道路交通相比其他工作日会更拥堵,这为我们提供了一个识别交通拥堵的独特指标。通过使用双重差分模型排除了大量干扰因素后,我们对北京市35个空气质量监测站点PM2.5浓度逐时数据的分析发现,在限行尾号为4和9的工作日,高峰时段与非高峰时段的PM2.5浓度差异,比其他工作日的差异高出9.46%。交通拥堵显著降低了空气质量。

关键词: 空气污染, 交通拥堵, 空气质量, 双重差分