Quick and simple way:
Click on Trainz Settings while in Driver or Surveyor.
Click on Interface Settings on left.
Uncheck Cabin sway in internal view:
More complex way:
Clone the track you like.
Update this line or add it in if it doesn't exist to your favorite track. Do not put this inside any container, meaning anything that has { } brackets. Keep the spacing the same as it is in the config.txt file.
track-condition "0.50"
This is an example with the condition set to 50%, the default setting for track.
Less than this and the track rougher. 0.01 is 1% and that's really, really bumpy. I've used this for really bad sidings. I've also used 0.05 for really bumpy, rolling coal and freight branches where doing anything more than 10 mph is deadly.
There's no derailment, but it sure looks immanent.
You can now use the bulk update utility to update your already placed track in one fell swoop.