Which vehicles are not allowed to overtake here?

Your answer is correct. This traffic sign in Germany means that trucks and trucks with trailers exceeding 3.5 tons are not allowed to overtake other vehicles here. It is designed to prevent heavy vehicles, which take longer to accelerate and require more space, from overtaking in certain areas where it could be dangerous or cause traffic disruption. However, truck tractors (articulated trucks without a trailer) and passenger cars are not restricted by this sign and may overtake if it is safe to do so. Understanding this sign helps ensure safer and smoother traffic flow, especially on roads where slower overtaking by heavy trucks could cause hazards.