SIGNIFICANT FACTORS IN TRUCK RIDE QUALITY. VOLUME I. SUMMARY REPORT

The objective of this study was to identify factors leading to significant differences in truck ride quality for a representative sample of long haul trucks in regular commercial use. Representatives of industry and labor organizations were contacted in order to obtain their assessments of key problem areas, and the state of the art in ride assessment technology was reviewed. A new experimental methodology was evolved which avoided most of the problems of earlier research. Data acquisition and analysis systems were developed for obtaining accurate, repeatable, and reliable ride data during in-service truck operations. In-service measurements were made with a typical variety of truck types, tires, seats, loads, speeds, roadways, and drivers. An array of in-cab data was tape recorded, with measurements being made in several short bursts for each of several roadway pavement categories and operating conditions. The IRIG Standard FM tape recordings included speed and six channels of in-cab vibration, cab floor and seat accelerations. Other recorded variables included: sound power level, air temperature, and driver and experimenter subjective ride ratings. The collected data were used to compute various ride quality measures, and include comprehensive statistics, spectra and ISO weighted measures. Preliminary correlations between objective and subjective ride measures were established. The dominant truck ride factors were found to be: pavement condition, wheel asymmetries, truck design and loading variations, and, to a lesser degree, cruising speed. No clear ride superiority was shown for any one type of tractor configuration, suspension, or seat. (FHWA)