Whole body vibration exposures in bus drivers: A comparison between a high-floor coach and a low-floor city bus

Low back pain (LBP) is common in occupational bus drivers and studies have shown a dose-response relationship between whole body vibration (WBV) exposure and LBP. Bus design may be an important factor in determining the WBV exposure a bus driver receives. The purpose of this study was to determine whether differences exist in WBV exposures between two buses commonly used in long urban commuter routes: a high-floor coach and a low-floor city bus. Each bus was driven over a standardized test route which included four road types: a newer smooth freeway, a rougher old freeway, a city street segment, and a road segment containing several speed humps. WBV exposures were calculated per ISO 2631-1 (1997) and ISO 2631-5 (2004) standards. WBV exposures were significantly higher in the high-floor coach bus on the road segment containing speed humps. There were primarily small differences between buses in WBV exposures encountered on the city street and freeway segments. With respect to the ISO 2631-1 and European Union's A(8) and VDV(8) action limit values, both buses could be operated on the smooth freeway without exceeding the 8-hour action limits but would have to be operated less than 8 h when operating on the other road types. On average, the seats only attenuated 10% of the floor transmitted vibration and amplified the vibration exposures on the speed humps. Due to the low vibration attenuation performance of the bus driver's seat, evaluating different types of seats and seat suspensions may be merited. Relevance to industry: Low back Pain (LBP) is one of the leading causes for workplace disability; therefore, it would be beneficial for employers and workers to minimize WBV exposures resulting in LBP. To reduce WBV exposures, buses should be assigned to appropriate routes and drivers should rotate across routes to vary continuous and impulsive exposures.