In order to avoid pressure and volume compensation as much as possible during measurement of the pressures of air spring units, the pressure in the air spring units (5, 6, 7, 8) is estimated prior to measurement of the pressures of the air spring units (5, 6, 7, 8) and is compared to the pressure in the air pressure accumulator (3). The higher of the two pressures determines the position of a 3/2 directional control valve (11) which separates the collector line (25) connecting all air spring units (5, 6, 7, 8) from the air pressure accumulator (3) or which connects it to as small a chamber volume of the supply system as possible.