Whole-body vibration exposure in metropolitan bus drivers.

BACKGROUND Back injuries are common in transit drivers, and can result in substantial direct and indirect cost to the employer and employee. Whole-body vibration (WBV) is one risk factor for drivers. Standards have been adopted (ISO 2631-1) to guide researchers in measuring and analysing WBV levels. Lately, a new standard has been added (ISO 2631-5) that takes impulsive exposures into account. AIMS The aims of this study were to determine the levels of vibration for bus drivers using both ISO 2631-1 and 2631-5 standards, and whether there are differences in vibration levels and seat transmissibility between different road types. METHODS Thirteen bus drivers drove a 7-year-old bus, instrumented to measure WBV in the seat and floor. The 52 km long test route included freeway, city streets and speed humps. Additionally, for comparison, a subset of five drivers also drove a car over the same route. RESULTS Road type had a significant effect on all the vibration parameters. Based on exposure limit values in the standards, the continuous z-A (w)(8) exposures exceeded the limit value on freeways, and the impulsive z-VDV(8) and S (ed) exposures were above limit values in city streets and speed humps. Bus WBV exposures were about twice as high relative to the car and the bus seat amplified rather than attenuated WBV exposures. CONCLUSIONS Bus drivers are potentially being exposed to daily vibration levels higher than recommended especially on certain road types. The current seat in this study does not attenuate the vibration.