[Fatigue and low-back pain of freight-container tractor drivers. Correlation with ergonomic factors]

An ergonomic checklist was prepared to examine safety and comfort of freight-container tractors. With this checklist, 533 tractor drivers were asked to evaluate the tractors to which they were exclusively assigned. In order to check the objectivity and the validity of the results, the correlation between the evaluation of the items on the checklist and the corresponding dimensions on 10 tractors was studied. Also, a multivariate analysis based on quantification theory was done to examine the correlation between the ergonomic items on the checklist and the drivers' low-back pain or fatigue symptoms of the upper and lower extremities. The main results were as follows: 1) A high correlation was observed between the evaluation of items on the checklist and the corresponding dimensions of the tractors. 2) Many items on the checklist received a poor evaluations, indicating that there are many ergonomic problems with freight-container tractors. 3) The analysis by the quantification theory showed high correlation ratios between the items in the checklist and the drivers' fatigue symptoms of the upper and lower extremities. These correlation ratios were: arm fatigue when holding the steering wheel (0.51), arm fatigue in operating the gearshift lever (0.65), arm fatigue from opening and closing the windows (0.46), leg fatigue from operating the pedals (0.58), and low-back pain during the last two months (0.31). These showed that more than 50% of the fatigue symptoms could be explained by the ergonomic aspects of the tractors. 4) The rate of dissatisfaction with the current tractors was 82.9%. According to the analysis by the quantification theory, the correlation ratio between the items in the checklist and the rate of dissatisfaction for the current tractors was 0.66. 5) The foregoing results indicate that ergonomic improvement of the freight-container tractors is a matter of urgency. This should reduce the drivers' fatigue and elevate the rate of satisfaction with the tractors. 6) However, for the prevention of the drivers' low-back pain and fatigue symptoms, improvement of the ergonomic conditions of the tractors and the drivers' working conditions must be undertaken at the same time.