While there isn't a single official "Bus Mod version 1.15.1," this specific version number typically refers to a stable legacy build of Euro Truck Simulator 2
the bus mod (and any required passenger/physics mods). euro truck simulator 2 bus mod version 1.15.1
Always back up your original ETS2 folder before modding. While there isn't a single official "Bus Mod version 1
Version 1.15.1 — Technical Context and Expectations euro truck simulator 2 bus mod version 1.15.1