I dont know if this is to do with the cars, or the track, but the brick walls sometimes disappear when you look at them through the windscreen. See the pics ...

Another alpha issue with the car shader.

..a weird one then; because the brick walls dont use alpha layers..

so its deffinetly something up with the windows

but its weird that the land behind it on the first picture appears but the wall doesn't

But it doesnt always do it ...

I suppose this is the same bug as the dissapearing cones one, they are visible through the small visor screen in the FOX, but when you touch them they dissapear in the screen but are still visible outside the screen.