Modeling an irregular track

Hello everyone,
I’m modeling an irregular track for a cartoon car racing game (Unity3D). The track has many curves, ups and downs.
I’ve made a track tile, and using an array modifier I have generated the circuit using a bezier curve.
The problem is the collider. I would like to use the mesh collider of Unity 3D but if I put the car on the track I notice that the perceived collider by the car is not very smooth. How do you suggest to fix this?

I also tried to make a second track with more subdivision using it just as a mesh collider (without mesh renderer) but the result is almost the same.

Thanks in advance, I’m pretty noob with Blender.

Can you strip it down to a flat path with no thickness or raised edges, shrinkwrap it to the track, apply the modifier, extrude another long face at the front and end, select all and inset to make the edges for the raised sides, solidify and apply, select the top faces of the edges that will be the raised sides, separate them into another mesh, solidify them upward and apply, join the edge mesh and the track mesh, select all and remove doubles.