I have completed the basic bus station ground by adding some small remaining areas (for example a parking area under the bridge) so I consider it to done for now.
Some extra details like tarmac patches, sewers etc. will be added to all roads at once later.
Now I can move on and start to add another roads.
Currently I am trying to highlight all important road borders / lines / marks with Blender’s Grease Pencil, it saves a lot of time while modeling!