A task analysis was carried out using structured survey questionnaires that were sent out to a random group of sprayer operators in Manitoba, Canada. Twenty sprayer operators ( < 25 yr(5%), 26-30 yr(15%), 31-40 yr(10%), and 41-60 yr(70%)) participated in this study; on average they had 21 yr of driving experience, but only an average of 2.7 yr of experience with GPS guidance systems. The important elements of the eye-glance behaviour and visual workload included looking at the horizon, booms, lightbar, mapping system, application display, tachometer, temperature gauge, and pressure gauge. The contributing factors for physical workload were: solenoid on/off, boom height control, sprayer pump on/off, hydrostatic and transmission control, and throttle. Factors influencing the mental workload included: operating the tractor/self-propelled unit, searching for guidance information, monitoring rate controllers and pressure gauges, controlling the sprayer pump, GPS system, and boom height controls, and talking on cell phone. Guiding the tractor involved the highest amount of mental workload. Fatigue indicators identified were sore eyes, poor concentration, restlessness, yawning, moodiness, boredom, and sleeping at the wheel.
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