This International Standard specifies, in accordance with ISO 10326-1, a laboratory method for measuring and evaluating the effectiveness of the suspension of operator seats on agricultural wheeled tractors. It also specifies acceptance criteria based on the test results, while defining the input spectral classes relating to three classes of agricultural tractor with rubber tyres, unsprung rear axles and no low-frequency cab isolation - those of up to 3 600 kg (class 1), those of from 3 600 kg to 6 500 kg (class 2), and those of over 6 500 kg (class 3) - each of which defines a group of machines having similar vibration characteristics. The method tests the effectiveness of the seat suspension in reducing the vertical whole-body vibration transmitted to the operator at frequencies of from 1 Hz to 20 Hz. It is not applicable to vibration reaching the operator other than through the seat (e.g. that sensed by the operator’s feet on the platform or control pedals or hands on the steering wheel). NOTE The tests and criteria defined in this International Standard are intended for operator seats used in agricultural tractors of conventional design. Tractors with design features such as isolated front or rear axles or both and low-frequency cab suspensions, which result in significantly different vibration characteristics, can be tested in accordance with ISO 5008 to determine a whole body vibration emission value or using other standards developed for measuring and evaluating the effectiveness of the seat suspension on such vehicles.