Which vehicles are not allowed to overtake here?

This traffic sign indicates a general overtaking ban for trucks. According to German traffic rules, trucks and truck tractors with a permissible total mass exceeding 3.5 tons are not allowed to overtake other vehicles in this zone. The reason is to improve traffic safety and flow by preventing slower, heavier vehicles from overtaking.

Cars, however, are not affected by this sign and are allowed to overtake as usual. So, the ban applies specifically to larger trucks and truck tractors meeting the weight criteria, which is why both 1 (trucks over 3.5 t) and 2 (truck tractors) are correct answers.

Remember, this sign targets heavy vehicles rather than all motor vehicles, emphasizing safety on roads where overtaking by large vehicles could be dangerous.