## 7 Conclusions and Implications  
Understanding the relationship between high-speed rail and the level of green technology innovation is critical to investigating how transportation infrastructure will shape the future development of Chinese green technology innovation. In this paper, we applied panel data from 284 prefecture-level and above cities in China between 2004 and 2013 to construct a two-way fixed-effect model to evaluate the influence of high-speed rail service supply on green technology innovation. The regression results suggest that the supply of high-speed rail services can considerably promote the capability of urban green technology innovation. In addition, we creatively introduced the collaborative agglomeration of manufacturing and producer services to clarify the intermediary effect of the industrial collaborative agglomeration between high-speed rail and green technology innovation through the mediating effect model. Furthermore, from the heterogeneity tests, we found that the effects of green technology innovation brought about by high-speed rail are varied in different types of cities. Therefore, this article proves that high-speed rail considerably advances the level of green technology innovation through industrial collaborative agglomeration. The basic results are consistent with the previous findings that high-speed rail speeds up the flow and diffusion of human capital and innovation factors between cities, thereby stimulating the development of urban green technology innovation. Meanwhile, by causing the collaborative agglomeration of manufacturing and producer services, high-speed rail expedites the formation of green technology innovation from three aspects: the industrial linkage effect, scale effect, and knowledge spillover effect. However, the results suggest that the effect of green technology innovation brought about by high-speed rail is not significant in eastern China. The possible reason is that most cities in the east are cities with advanced green technology innovation, and there is no room for additional growth in the short term. For cities in the central and western regions, high-speed rail is an essential catalyst for encouraging the growth of urban green technology innovation. Besides, after the further analysis of heterogeneity, we propose that cities that relatively lack government \begin{table}
\begin{tabular}{c c c} \hline \hline  & **(1)** & **(2)** \\ \hline
**Variables** & **FirstStage** & **2 SLS** \\ \hline InAltitute & \(-0.265\)*** & \\  & (\(-3.04\)) & \\ InHSRFreq1 & & 0.833*** \\ Observations & & (2.80) \\ R-squared & & \(-0.207\) \\ Control Variables & Yes & Yes \\ F & & 24.51 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: The results of the regression using the instrumental variable. support and that are relatively backward in public cultural infrastructure are more able to benefit in terms of their green technology innovation from the supply of high-speed rail services. This study supplements the content related to the advance of green technology innovation, but there are some limitations. Firstly, this article only conducts empirical tests from the perspective of industrial collaborative agglomeration, leading to a lack of a comprehensive and detailed investigation on the mechanism of high-speed railways. Secondly, the spatial spillover effect of the high-speed railway is not taken into account, which may lead to a deviation in the estimation results. Finally, due to the availability of data, this article fails to give a more detailed classification of green patents. In the future, the relationship between the transportation network and various green patents will be discussed in a more comprehensive and in-depth way. According to the main research conclusions, we propose the following recommendations by combining the status quo and characteristics of China's development. Firstly, China should continue to vigorously develop rapid transportation, expanding the coverage of high-speed rail services within China.