Analysis of an Intervention to Reduce Truck Drivers' Exposure to Whole-Body Vibration

Thesis (Master's)--University of Washington, 2016-06Introduction. The high prevalence of low back pain in drivers of commercial motor vehicles is well-documented. A number of interventions to reduce low back pain in commercial motor vehicle operators have focused on reducing exposures to wholebody vibration (WBV). Objective. An intervention to be evaluated for the trucking industry is an air-filled ballistic seat pad designed to reduce exposure to WBV. The effectiveness of the seat pad in semi-trucks has not yet been established. Results from a previous pilot study involving 12-ton and 16-ton vibratory rollers used by Seattle Public Utility drivers suggest that the seat pad is not effective at very low speeds (1-3 mph). Methods. The current study measures, characterizes and compares WBV exposures in nine truck drivers who operated their trucks over the same roads. WBV exposures were compared between their existing air-suspension seat and the air-filled ballistic seat pad which sat on top of their existing seat. This study uses a Wilcoxon signed rank test to compare the seat pad’s effectiveness in reducing WBV exposures relative to their existing air-suspension seat. Results. Overall, the truck drivers' vibration exposures were above daily vibration action values set by the International Standards Organization (ISO) and the air-filled ballistic seat pad did not significantly reduce WBV exposures relative to the WBV exposures experienced with their existing air-suspension seat. Conclusions. In the semi-trucks evaluated in this study, the air-filled ballistic seat pad was not effective in reducing WBV exposures. The seat pad has been shown to be effective in reducing WBV exposures in public transportation buses and cars. The answer for why the air-filled seat pads were not effective in semi-trucks may lie in a future analysis of the power spectral densities, which shows the vibration exposures as a function of frequency. Buses and cars produce more high frequency vibration energy, and the air-filled seat pad has been shown to be effective in these vehicles when travelling at moderate to high speeds. Trucks may produce less high frequency vibration energy, and this may have diminished the air-filled seat pad’s effectiveness in the semi-truck evaluated in this study