Improving work load and comfort of operators on modified hydraulic excavators in rail road maintenance

In small-scale projects of mechanized maintenance of rail roads special equipped hydraulic excavators (HE) are used in several maintenance tasks. One task concerns the exchange of the old crossbars and ballast under the rails by new materials (MCE-task). This task requires high precision of the HE-operators. Inaccurate controlling the machine movements may have safety consequences for the rail road workers around. Signals of fatiguing in this group of operators instigated a more detailed assessment of their work, work load, mental strain and physical discomfort. The organizational and ergonomic factors studied were: work practices, work-recovery schedules and cabin and/or operating controls. Work satisfaction and health as possible confounders for fatiguing effects in this group were assessed as well. In total 16 out of 17 experienced operators of 3 leading companies in the Netherlands participated in the study. In a pilot study, data of 4 operators were sampled during full day and night shifts, i.e. work strain ratings and heart rate-variability was measured. Several postures and movements were assessed and interviews were held, resulting in a tailor-made questionnaire on work and fatigue related problems. Main conclusions were: the mechanized crossbar exchange task is more straining than other operator's rail road maintenance tasks. In the second half of the shifts fatigue symptoms may rise too high, particularly during special project circumstances. Inherent ergonomic shortcomings in the technology chosen and in the cabin design lead to unnecessary fatiguing. Improvements of the work-rest schedule and the techniques used are recommended to increase the operator's comfort and the safety of his coworkers.