I was trying to figure out how you could rig this most effectively, simply put, two rails with an object moving along the path (using the curve modifier), each should have indipendant forward/backward motion in the rig.
https://imgur.com/a/ZlNyF0T
Ive been out of the game for a while, any suggestions would be welcomed!
What Martin said. The only thing I would change on the modifier is check fixed position. The offset will now be 0 to 1 with 0 being start of curve and 1 being end of curve. Then you can keyframe the offset or use a drive pointing to a bones location. The you can just move the bone 1 meter to move it to the end of the curve.
The skill to do the driver method is covered in the shapes course.