American Truck Simulator [v 1.36.1.18s Dlcs] ... -
Version 1.36 added detours and updated anti-aliasing . If you are building a map mod, you'll want to leverage the newer assets found in the Utah and Washington directories. [1, 4]
To help you "develop a piece" (whether that is a mod, a custom skin, or a map expansion), here is a quick technical breakdown of that specific version: American Truck Simulator [v 1.36.1.18s DLCs] ...
Ensure your .scs files are placed in Documents/American Truck Simulator/mod . Since 1.36, the game is more sensitive to mod priority in the "Mod Manager" to avoid crashes caused by old DX9 assets. [5, 6] Version 1