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The safety of front-end loaders should be given the highest priority in research since they have been involved in 27% of fatal accidents and 22.4% of non-fatal accidents in surface mining, second only to trucks. Operator safety was considered to depend on the workload, environmental stressors and the subsequent deterioration in performance. Operator workload intensity was established by analyzing tasks and stressors in each segment of the cycle. Deterioration in performance was measured by increases in reaction time and by frequency of errors. A physical simulator was designed and constructed to generate operational task demands in a controlled laboratory environment. Tests were performed under normal and stress conditions and the results were compared. Physiologic responses of oral temperature, pulse rate and blood pressure were measured before testing, after normal and finally after stress conditions. The heart rate was measured continuously during the experiment. Subjective reporting was elicited by questionnaires which dealt with the subjects well-being and the simulator design. Results indicated an increase in reaction time and number of errors with time and intensity. The physiologic responses were also elevated. Subjective evaluations again showed an increase in the level of discomfort and clear symptoms of stress and fatigue. The statistical significance of the results were substantiated by an analysis of variance. The results correlated with each other and supported the hypotheses underlying the study. An extensive two part review of literature examined the man-machine interface of front-end loaders and the human performance criteria. The first part assisted in developing the workload intensity profiles and the second part assisted in formulating the appropriate theories and relationships.