Is your feature request related to a problem? Please describe.
no

Describe the solution you'd like
加入可自定义的轨旁标志（例如 限速XX公里 等）并可以自定义其样式和内容。
Add customizable trackside signs (e.g. speed limit XX km, etc.) and their style and content can be customized.
自定义的（WAV文件）列车接近，发车，列车车内广播。
Customized (WAV file) train approach, departure, train car announcements.

Additional Information
如果可以实现的话，我希望可以在之后的版本加入他们。
如果这些功能太难以实现的话，请忽略我的建议。
I hope to add them in a later version if it is possible to implement them.
If these features are too difficult to implement, please ignore my suggestion.

But I think these functions can be done more simply through the graphical interface of mod @cherbert @kettle-7

But I think these functions can be done more simply through the graphical interface of mod @cherbert @kettle-7

Your second suggestion can already be done with command blocks, a resource pack and OGG Vorbid media files.

To be fair, so can the first.

This can be implemented as kettle and cherbert mentioned. Thanks for your suggestions!