Rail - Behavior Property
Choosing “Rail” as the behavior property in the scene editor enables you to make the object move as if it was on the rails. The following is a screenshot taken from a project that a locomotive moves on a square path with round corners.
The locomotive doesn’t change its orientation through the path.
If you set the behavior as “Rail”, the model changes its orientation so that it keeps its ends on the path.
The following movies show how it moves by the option, and you can see the difference.
Normal
Rail
“Galaxy Express 999” by SeaGate