I have noticed that you can gain speed infinitely. Maybe, you should use the law of conservation of energy in your physics calculations so that the movement of the trains is more realistic. you would need to use friction, momentum, gravity, and the force of the engine as forces. Also, the power of the engines should not be applied linearly and should have a maximum or plateau point. In other words, the maximum speed should not be exceeded unless going downhill.

Physics are slated for a significant rewrite.