【论文摘要】This paper investigates how transportation infrastructure projects facilitate research collaboration across cities and promote innovation. Exploiting the construction of high-speed rail (HSR) network as a plausibly exogenous shock, we find that innovation in less-developed cities significantly and quantitatively improves after the cities are connected to more developed cities through the HSR network. Of all mechanisms considered, incremental research collaboration can explain 2% to 12% of the innovation improvement. The empirical results imply that even under the “promotion tournament model “of spatial competition structure, cities can still mutually benefit through research collaboration.