Variance of whole-body vibration of seated person in passenger car

The variability in whole-body vibration (WBV) of a seated person measured in the passenger car was evaluated. The vibration variability was evaluated as a function of the International Roughness Index (IRI). Vibration was measured on 58 test vehicles of 6 different categories. A two-parameter regression function relating the overall vibration total value to its 95% confidence interval and IRI was estimated. The identified regression function may help detect the IRI threshold. The IRI threshold could be derived from the boundaries of comfort reactions to vibration environments, as specified in ISO 2631-1: 1997. Calculation of a 95% confidence interval for the measured overall vibration total value at the seat surface showed that a single IRI value can correspond to vibration values that span up to comfort levels according to ISO 2631-1:1997.