Which vehicles have to maintain such a great distance between them and the vehicle ahead when not inside a built-up area, that an overtaking vehicle can pull back into lane?

The selected combination of vehicles that must maintain a large distance when not inside a built-up area is correct because it ensures safe overtaking maneuvers.

According to German traffic regulations, trucks with a gross vehicle weight rating in excess of 3.5 tons and combination vehicles longer than 7 meters need to provide sufficient space for overtaking vehicles to safely re-enter their lane. This requirement is crucial for road safety, as it prevents accidents during overtaking and allows for better traffic flow.

The reason trucks with a gross vehicle weight rating up to 3.5 tons are not included is that they typically have less impact on traffic dynamics compared to larger vehicles. Thus, they do not need to maintain the same distance to allow for overtaking as the heavier trucks and combinations. Understanding these distinctions helps drivers ensure compliance with traffic laws and promote safety on the roads.