Ride Index Structure and Development Methodology
|Publication Date:||1 October 2013|
This recommended practice defines methods for the measurement of periodic, random and transient whole-body vibration. It indicates the principal factors that combine to determine the degree to which a vibration exposure will cause discomfort. Informative appendices indicate the current state of knowledge and provide guidance on the possible effects of motion and vibration on discomfort. The frequency range considered is 0.5 Hz to 80 Hz. This recommended practice also defines the principles of preferred methods of mounting transducers for determining human exposure. This recommended practice is applicable to light passenger vehicles (e.g., passenger cars and light trucks). This recommended practice is applicable to motions transmitted to the human body as a whole through the buttocks, back and feet of a seated occupant, as well as through the hands of a driver.
This recommended practice offers a method for developing a ride performance index but does not specifically describe how to apply this index to assessment or comparison of specific vehicles.
NOTE: This recommended practice may also be applicable to other types of ground vehicles (e.g., medium and heavy duty road vehicles) with seated occupants having similar seating posture, occupant/vehicle interfaces, and vibration magnitudes, frequencies, and durations as light passenger vehicles.
The primary purpose of this recommended practice is to define methods of quantifying human sensitivity to occupant motion and vibration in passenger cars and light trucks based on objective measurements of acceleration and sound in order to simplify and standardize the reporting, comparison and assessment of motion and vibration conditions. It contains methods for the evaluation of vibration containing occasional large peak values (i.e., having large crest factors). Human sensitivity is quantified in terms of predicted subjective discomfort levels, based on suitable psychometric and statistical methodologies. Passenger cars and light trucks and vans expose occupants to periodic, random and transient mechanical vibration which can cause various levels of subjective discomfort. This recommended practice does not contain vibration exposure limits and does not address potential effects of motion and vibration on health and safety, or on motion sickness, which involve different phenomena. This recommended practice does not address the potential effects of intense vibration on human task performance since these involve different phenomena which depend critically on the biomechanical and ergonomic details related to the operator, the situation and the task. Appendix C provides rationale for the assessment of human discomfort due to motion and vibration. More information may be obtained from the scientific literature, a portion of which is listed in 2.2.1 and Appendix B. Motion and vibration is often complex, contains many frequencies, occurs in several directions and changes over time. The effects of motion and vibration on human discomfort may be manifold. Exposure to whole-body vibration causes a complex distribution of oscillatory motions and forces within the body. There can be large variations between subjects with respect to discomfort effects. Whole-body motion may cause sensations (e.g., discomfort or annoyance). The presence of oscillatory force (i.e., vibration) with little whole-body motion may cause similar effects.