When must a car with trailer driving outside built-up areas on roads with only one lane for each direction keep a sufficient distance from the car in front so that an overtaking vehicle may pull in?

If you are driving a car with a trailer outside built-up areas, and your vehicle combination is longer than 7 meters, you must keep enough distance from the vehicle in front so that another vehicle overtaking you can safely pull back in. This rule is in place to allow overtaking vehicles enough space, which is especially important because longer vehicles take up more road space and can make overtaking more difficult and dangerous. Always make sure to leave a large enough gap when your vehicle and trailer together exceed 7 meters in length.