Abstract: A road tractor semi-trailer combination 1 is equipped with a system for detecting the position of a road tractor relative to a semi-trailer. This system comprises a magnet 13 which is accommodated in the center of the bottom of the kingpin and a sensor unit 11 which is fixed to the bottom of the fifth wheel 9. The sensor unit can be displaced between a resting position at a distance from the magnet where the position of the magnet cannot be detected, and an operating position at a distance from the magnet where the position of the magnet can be detected indeed. The fifth wheel is equipped with a handle for displacing a locking pawl which locks the kingpin in the fifth wheel in coupled state of the road tractor and the semi-trailer. This handle is connected via a pulling cable to the sensor unit for displacing the sensor unit to the operating position simultaneously with the displacement of the locking pawl.

Abstract: A road tractor semi-trailer combination 1 is equipped with a system for detecting the position of a road tractor relative to a semi-trailer. This system comprises a magnet 13 which is accommodated in the centre of the bottom of the kingpin and a sensor unit 11 which is fixed to the bottom of the fifth wheel 9. The sensor unit can be displaced between a resting position at a distance from the magnet where the position of the magnet cannot be detected, and an operating position at a distance from the magnet where the position of the magnet can be detected indeed. The fifth wheel is equipped with a handle for displacing a locking pawl which locks the kingpin in the fifth wheel in coupled state of the road tractor and the semi-trailer. This handle is connected via a pulling cable to the sensor unit for displacing the sensor unit to the operating position simultaneously with the displacement of the locking pawl.

Abstract: A road tractor semi-trailer combination is equipped with a system for determining the position of a road tractor relative to a semi-trailer. A king pin is fitted to the bottom of the semi-trailer and a unit is fitted to the bottom of the fifth wheel coupling present on the road tractor. The bottom of the king pin has a recess into which a pivot forming part of the unit can be inserted. The pivot has the shape of a screwdriver and the recess has a shape congruent with the pivot.