Whole Body Vibration Exposure and Seat Effective Amplitude Transmissibility of Air Suspension Seat in Different Bus Designs

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A number of studies have shown that whole body vibration (WBV) exposures contribute to low back pain in vehicle operators. Bus design may be an important factor in determining the WBV exposures that a driver receives. The purpose of this study was to determine whether differences exist in WBV exposures among three buses commonly used in long urban commuter routes: a high-floor coach bus, a low-floor coach bus, and a low-floor articulating bus. Each bus had the same new air-suspension installed and was driven over a standardized test route which included four road types: a smooth freeway, a rough freeway, a city street segment, and a road segment containing several speed humps. WBV exposures were evaluated per ISO 2631-1 action limits for acceptable WBV exposure levels. In this study, there were statistically significant differences among buses in WBV exposures. The high-floor coach bus had the highest fore-aft (x-axis) exposures, the low-floor articulating bus had the highest lateral (y-axis) exposures and the low-floor coach bus had the highest vertical (z-axis) exposures. With respect to ISO action limits, the z-axis WBV exposures did not exceed the 8-hour action limit (0.5 m/s2). The study also found that the air suspension seat did not perform well in the coach buses. The air suspension seat transmitted 92% of the floor measured vibration to the seat of the operator on the high-floor coach bus, 88% on the low-floor bus, and 76% on the low-floor articulating bus. Due to the low vibration attenuation performance of the air suspension seat, an evaluation of the different types of seats and seat suspensions may be merited in future research.