Is your feature request related to a problem? Please describe.
Now the trains is really cool than anytime before. To make it better, we should add some physical behavior to make it much more real.

Describe the solution you'd like

1. Doppler effect. Now the train sounds use fade-in and fade-out to simulate it, but it cannot works well especially on some long trains.
2. Superelevation. Trains, especially high-speed train will be elevated for 120mm-150mm to make the train balanced.
3. Air-conditioner sounds. The sound of train is not only the motor-sound, also air-conditioner, broadcast and passengers.

Additional Information
The superelevation should can be setting of the custom model. It can helps us make tilt trains like X2000.

I think you are looking for an advanced Train Simulator. Have you forgotten this is Minecraft? The developer is restricted to the capabilities of Minecraft. Which has awful sound capabilities.

OK. Because of the poop code of Bugjump, sound capabilities is not necessary at present.
(In addition, Real-Train-Mod has invented the way to have a better physical behavior.)

If you are more interested in that then just use Real Train Mod

The two mods exist for very different purposes

I think you are looking for an advanced Train Simulator. Have you forgotten this is Minecraft? The developer is restricted to the capabilities of Minecraft. Which has awful sound capabilities.

Air conditioner sounds will be gradually added as we migrate to BVE sounds. Train swaying has now been added and is slowly being improved. I will keep this open for the doppler effect suggestion.