A simple tutorial to make roads on a mountain, this is just 1 of the methods to achieve this. There are many other ways but personaly this one is the easiest.

Remember 3ds max uses Plane but the correct spelling is Plain. This will help you in life

Create a Plane in 3ds max. Make sure you have enough faces to create smooth mountains.



Convert the Plane to Editable Mesh and click Vertex as the selection.
Go down and enable soft selection.



Once soft selection is enabled simply click on the vertex points (blue dots) and move them up/down/left/right to create your mountain.
Note: Soft Selection is good for simple hills, if you wish to have rough terrain I suggest you learn to use Displace.




Now go to selection tab and create a new Line under splines.



Go to Top View and draw your road on your plane. You will eventually work out the line tool if you have not used this
before.



Convert your line to Editable Spline.



Place a check in "enable in viewport" it is also better to use the rectangular settings.



You will now see your road/path that looks like a wall.



Adjust the length of your road so it overlaps with every part of your mountain (lowest point and highest point)



Convert your road/path to editable mesh.



Select your Plane, go to compound objects then click boolean.



Make sure cut>refine is selected. Click "Pick operand B" then click on your Road/path.



You will now see that your road/path model has sliced your plane.



Now Convert the entire model to editable mesh again.



You can now texture your road/path with smooth edges.