Evaluation of Noise Level, Whole-Body Vibration, and Air Quality inside Cabs of Heavy-Duty Diesel Vehicles

Abstract

Heavy-duty diesel vehicles were measured for noise level, whole-body vibration from the driver's seat, and in-cab air quality while the vehicles were parked with engine idling at a rest area and while they were driven. These baseline data will help similar studies determine whether new truck designs have changed these conditions for drivers. Twenty-seven trucks (model years 2006 to 2008) from four manufacturers were tested. Results showed slightly higher noise levels driving on the Interstate versus driving on the state highway. However, overall in-cab noise levels were found to be lower than occupational exposure standards. Evaluation of seating vibration used ISO guidelines. Average vibrations in the x-, y-, and z-axes of the seats were generally found to be well below European Union standard exposures for an 8-h driving day. Inferior road pavement conditions were thought to have contributed to higher vibrations in a few trucks where several instances of the vibrations exceeded the standards. For most trucks, the likely comfort reaction from the vibration magnitude of the driver's seat was “a little uncomfortable.” Air quality was determined by measuring in-cab concentrations of carbon monoxide (CO), oxides of nitrogen (NOX), and particulate matter with less than 2.5 microns aerodynamic diameter (PM2.5). Results indicated a tendency of trucks to self-pollute the cabs during periods of extended parked idling. Although overall CO and NOX concentrations were well below occupational exposure levels, PM2.5 concentrations during several parked-idling scenarios were higher than U.S. Environmental Protection Agency limits for ambient monitoring standards. During driving on public roadways, in-cab concentrations were lower than those measured during the extended parked-idling conditions.