Which vehicles are allowed to use the special lane marked like this?

You are correct. This traffic sign indicates a lane reserved exclusively for regular buses. According to German traffic rules, only these buses are allowed to use this lane to ensure faster and more reliable public transport. Trucks and cars are not permitted to drive in this lane. This helps reduce congestion and delays for public buses, improving overall traffic flow and public transport efficiency. Remember, if you see this sign, you must keep clear of that lane unless you are driving a regular bus.