High-Speed Rail and Scientific Collaboration. Evidence from China

China’s high-speed rail (HSR) network, initiated in 2008, now covers nearly all regionsof the country. This paper analyzes the effect of HSR connection on inter-city scientific collaboration and examines whether this e!ect varies systematically with the complexity of scientific fields. Combining the universe of HSR openings between 2008 and 2020 with OpenAlex publication records, we construct a panel spanning 33,793 Chinese city pairs. Using a staggered difference-in-differences estimator, we find that HSR increases co-publications among city-pairs with existing collaborative ties by 35.2 percent at the city-pair level. Disaggregating across twenty scientific fields, we show that this effect is quite heterogeneous. Field-level treatment e!ects range from 19.8 to 45.1 percent, and their magnitude is positively and significantly correlated with average team size -a proxy of the fields’ complexity. These results are consistent with the view that face-to-face interaction is still important for knowledge production requiring deep divisions of cognitive labour, and they carry direct implications for the design of transportation and innovation policy.