The road simply looks weird as the picture below shows. It's impossible to build a road manually on a double-height slope (even with public service), so why does it generate like this?
It is intended that it is impossible to build roads over double-height slope.
Normally the map generation don´t build double-height slope, if you select a map with a number.
But since the improvement of ceeac for loading maps from .ppm files such steep terrain is possible.
Because coding of map generation is much older then the coding of double-height slope, i think the check was forgotten to adapt to double-height slope.