Sphere trace not detecting spline meshes


I cannot figure out why my sphere traces from my vehicle are not being blocked by my procedurally generated spline meshes.

The road meshes are set to BlockAll collision preset with simple collision, yet the sphere traces from my vehicle do not interact with my road meshes whatsoever. I have been digging into the collision channels and presets in the project settings, but I’m not sure what I’m doing wrong. The sphere traces work fine if I put the car down on the terrain or a plane, but not on these road meshes.

Any help would be appreciated! Please see screenshots.