I think you are probably overthinking this and trying to make a simulation of a rollercoaster instead of making an animation of a rollercoaster. This would be very difficult if not impossible in LW. The dynamics are just not robust enough.
Don’t base your dynamics off your full track geometry. Use ‘Make Path’ to lock it to your more complex geometry. ClothFX and a poly chain are good for controlling multiple cars.
One problem I see with your track. How does the rollercoaster get back to the top?




