is heard to second distance 19 is increased by a specified amount 25 a new minimum distance 27 results from this distance increase 25 new minimum distance 27 is selected such that a sufficiently large distance 23 to first vehicle 3 prevails when the stop warning is heard distance increase 25 by which second distance 19 is increased i e by which the originally specified minimum distance is increased to form new minimum distance 27 preferably lies in a range from 10 to 50 cm especially 15 to 25 cm e g 20 cm in order to obtain sufficient distance between vehicle 3 which delimits perpendicular parking space 1 along the side and vehicle 7 to be parked so that the driver is still able to open the door and exit after reaching the parked position it is furthermore preferred if the minimum distance in subsequent backward moves continues to be selected larger than second distance 19 however a smaller distance than new minimum distance 27 set during the first backward move is sufficient the minimum distance of the subsequent backward moves may be increased by 5 to 30 cm for instance especially 7 to 15 cm e g 10 cm in comparison with original minimum distance 19 this is generally adequate to obtain sufficient distance between vehicle 7 to be parked and already stationary vehicle 3 once the vehicle has reached its parked position to determine a meaningful distance increase 25 for the first backward move it is also advantageous if prior to the actual parking operation a determination is made as to the type of parking space in which vehicle 7.