any trailer designed to be coupled to a motor vehicle in such a way that part of it rests on the motor vehicle and that a substantial part of its weight and of the weight of its load is borne by the motor vehicle, a freight-carrying vehicle without motor power that is attached by means of a "fifth wheel" to a tractor, resulting in a tractor-trailer combination, haagis, mis on ette nähtud haakimiseks sadulvedukiga või eelikuga ja mis kannab sadulvedukile või eelikule üle olulist vertikaalkoormust