A DECADE OF IMPROVEMENT IN WHOLE-BODY VIBRATION AND LOW BACK PAIN FOR FREIGHT CONTAINER TRACTOR DRIVERS
✍ Scribed by K. Nishiyama; K. Taoda; T. Kitahara
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 168 KB
- Volume
- 215
- Category
- Article
- ISSN
- 0022-460X
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✦ Synopsis
The authors' study in 1983 revealed that the whole-body vibration of the tractor units of freight containers was most hazardous in the back-to-chest directions (x-axis). The allowable exposure time was considerably shorter than that for heavy duty trucks. The low back pain (LBP) among the drivers seemed to be due to the long working hours and the ergonomically unsound tractor design, as well as the vibration. A preventative measure was the introduction of a tractor cab suspended by an air spring instead of a steel spring. In 1992, a follow-up field study was conducted. A personal vibration exposure meter developed by us measured the whole-body vibration on eight tractors. Eighty-nine triplets matched with the age and the years of driving tractors answered a questionnaire evaluation of the ergonomics of their tractor units.
The comparison of the newest steel suspension vehicles to the old ones produced by the same motor company revealed that in the x-axis the vibration level had decreased by as much as 4 to 9 dB. Some tractors showed an increase in vibration in the buttocks-to-head direction (z-axis). However, such adverse changes seemed not to affect evaluations acccording to the fatigue-decreased proficiency boundary (FDP) and the exposure limit (EL) recommended in ISO 2631-1978. The present models, regardless of the type of suspension, changed the direction of the most hazardous vibration from the x-axis to the z-axis. However, the effect of the air-suspension was not so remarkable as expected. Among 40% of drivers seemed to exceed the FDP boundary during a day.
The questionnaire study showed an improvement in the ergonomic evaluation of the tractors. The air suspension models seemed to induce less LBP than the steel suspension models.