Creating looping scenery?

I’ve tried looking at posts similar to mine, but they aren’t necessarily trying to do what I’m trying to do here. I wanted to create an animated background for a menu I’m developing, and that involves creating a looping background with moving parts. Something like a train occasionally passing through, or a moving road.

What would be the best way to achieve this effect? Initally I was going to tweens to move the parts, but I’m worried they’ll desync at some point, since they’re all varying sizes. Additionally, tweens don’t seem to physically move the part, so welding all the parts to one main moving part won’t work either.
I’ve also considered moving the camera, but I would like some parts to be standing still. Moving the camera means everything moves.