Mesh extrusion overlapping triangles problem

I have a spline created that I use to generate a race track. It works very well, the problem is when I have really sharp curves, the sides of the racetrack are overlapped, and my mesh ends up with a distorted surface like so Image

The spline consists of vectors that don't overlap, but extending to the left and right, this happens. Do you guys have any solutions for this? Also, how to correct my UV coordinates to not be weird?

Is there something in Unity where it would create a mesh that "wraps" around another mesh?