Landscape spline multiple meshes

hi.
is it possible to add multiple meshes to a landscape spline segment so that both are there? say a road and a tunnel?
if i add another mesh to the spline’s mesh array it is only alternated randomly between the two.
thanks.

I am using this method but i’m running into an overlapping issue. It’s not splines but maybe it can help. I learned from watching this guys on YouTube: