How to define a vehicle is out of its racing path?

I want to find out that whether the vehicle is out of the road and if it is, restart the game, for instance, replace it in the middle of the road. And the problem is how can I know that? Should I set up the collision of the road? Or restart it when the vehicle is touching the box brush?

Volume below road that upon overlap resets vehicle, or volumes placed along road that find non-overlapping vehicle.