Use of 2D scatter to generate random cars on road lane

There are currently some limitations to use scatter (2D on surfaces) in order to generate random cars along a 3d road lane:

1- longitudinal slope

uphill/downhill slopes create opposite car facing direction

2- lateral slope (water drainage)

generated cars no longer follow road direction if lateral slope is introduced (scatter is unable to follow UV mapping)

That would be awesome to make it work!