Subways and Road Congestion Yizhen Gu, Chang Jiang, Junfu Zhang and Ben Zou∗ Abstract We study whether subways alleviate road congestion by examining 45 subway line launches in China and using detailed data on road speed. Our difference-in-differences estimation finds that in the first year after a subway line is launched, rush-hour speed on nearby roads in- creases by about 4%. The effect is most prominent in initially-congested roads and declines over distance to the new subway line. Evidence on road speed is corroborated with substitu- tion patterns among modes of transportation. Using auxiliary data from Beijing, we calculate that the time savings for each automobile or bus commute from faster speed is worth 0.1 USD. Keywords: Subway, congestion, public transit JEL Classification: R41, R42, L92 [Accepted for publication at American Economic Journal: Applied Economics.] ∗Gu: Institute for Economic and Social Research, Jinan University; email:
[email protected]. Jiang: Maps Open Platform Department, Baidu, Inc.; email:
[email protected]. Zhang: Department of Economics, Clark University; email:
[email protected]. Zou: Department of Economics, Michigan State University; email:
[email protected]. We would like to thank Seema Jayachandran and four anonymous referees for extremely helpful comments. We thank Richard Arnott, Victor Couture, Mark Jacobsen, Ajin Lee, Matt Turner, Cliff Winston, and participants at seminars and conferences at Brookings-Tsinghua Center, Fudan University, Harvard University, Huazhong University of Science and Technology, Jinan University, MIT, Michigan State University, University of Chicago, and Singapore Management University for helpful comments. We are grateful to the people at the Baidu Maps Open Platform department, in particular Tianqi Liu and Xiangmin Li, for providing and helping us with the data.