What is the maximum speed you are allowed to drive a bus with luggage trailer on main roads?

You answered correctly: the maximum speed allowed for a bus with a luggage trailer on main roads (Landstraßen) in Germany is 80 km/h. This rule is specific to this vehicle combination, as buses with trailers have stricter speed limits due to their longer braking distances, increased weight, and the need for greater traffic safety. Always remember to watch for lower posted speed limits, and that this 80 km/h limit applies unless signs or other rules set a lower speed. This helps ensure safety for passengers and other road users.