A system is provided for monitoring spacing during working operation between a first vehicle and at least one further self-propelled vehicle. A beam source is on one vehicle (source vehicle). A sensor arrangement on another vehicle (target vehicle) extends along a sensor axis. In a predetermined reference state, with the vehicles having a predetermined reference spacing apart, the beam source radiates toward the target vehicle electromagnetic radiation such that a predetermined sensor-axial reference detection region on the sensor arrangement is irradiated by the beam source. A change in the vehicle spacing results in a change, along the sensor axis, in the position of the detection region on the irradiated sensor arrangement, and thus in a change in the detection state of the sensor arrangement. Based on the detection state which depends on an actual spacing of the source and target vehicles, a spacing signal is generated with vehicle spacing information.