attach terrain to mesh

Hey,

I want to create a script which will kind of attach the terrain to my mesh (road mesh). So with attach I mean that the terrain raises to the height of that mesh so that when my player gets off the road there won't be a height difference.

So I already saw something like this in EasyRoad3d where the terrain gets adapted to the mesh. I actually have no idea how to start but if somebody has any idea what I would need to do that would be great