Abstract: A measuring arm (12) is attached to a frame (5a) supporting a screed (5). Height sensors (13) and (14) are attached to the measuring arm (12), and a height sensor (19) is also attached to the arm (18) of the screed (5). The spacing must remain constant between the rear end of the screed (5) and the height sensor (19), between the height sensor (19) and the height sensor (14), and between the height sensor (14) and the height sensor (13). A distance sensor to calculate the travel distance is provided on the tractor unit (1). The relative height Ho of both height sensors (13) and (14) to the screed (5) must always remain constant, regardless of the tilt of the screed (5) and the measuring arm (12). The sensors (13), and (14), and (17) are connected to the arithmetic unit (30). The height sensor (19) is connected to the arithmetic unit (40). The arithmetic unit (30) receives an output signal from the height sensors (13) and (14) and calculates the thickness of the pavement.

Abstract: An access alarming method and apparatus for activating an alarm in the event of the access of a working vehicle, such as a road roller, to an object, such as a worker, in the same working area as the vehicle. An ultrasonic wave transmitted by a transmitter on the object is received by a receiver on the vehicle. The received signal is processed and used to determine the relative position of the vehicle with respect to the object. An alarm is activated, and/or the vehicle is braked when it is judged that the object is within a hazard area determined in relation to the position and course of the vehicle.