Mesh Collider slow down the app

I have a simple straight road and put a mesh collider on it, and a car on this road. if I run it on iPad then it gives poor performance, app not running soomthly.

If I put box collider instead of mesh collider then its running smoothly and gives better performance on iPad.

How can I improve performance of app with the mesh collider, am I doing something wrong?

Your answers will be appriciable.

Thanks in advance!

Mesh colliders are the most expensive colliders possible. The more polygons your mesh has the worse it is. The performance is also very critical for mobile devices. I guess the road just has too many polygons to work as collider on iPad.

In generall you should only use mesh colliders when you have to. In many cases it is sufficient to approximate the shape of your gameObject with a capsule/cube/sphere.

If you have to use a mesh collider is always worth considering to make an additional mesh. This new mesh has roughly the same shape as the mesh on the gameObject but is less detailed. That way you use less performace on the collisions but maintain the same behaviour compared to using the original mesh.

All in all I’d suggest to lay box colliders over the road like you did before.