Evaluation of Mental Workload Associated with Operating an Agricultural Sprayer in Response to Three Different GPS Navigation Aids

Abstract

In modern agricultural spraying, the commonly used guidance aid includes a GPS lightbar and/or a GPS mapping unit. A lightbar display and a mapping display both present guidance information, but in different formats. A stacked display was developed with the intent of drawing on the advantages of both types of displays. The objective of this research was to identify the display that would produce the least amount of mental workload. Mental workload was measured by performance measures, physiological measures, and subjective rating scales. Performance measures included lateral root mean square error for driving performance and reaction time for secondary task performance. Physiological measures included two measures of eye-glance behavior. The subjective rating scale included the simplified SWAT scales. Sixteen male university students participated in this study. They were trained to drive an agricultural driving simulator. Performance measures clearly indicated that the driving performance and monitoring performance were highest for the lightbar display. Physiological measures also showed a similar trend: less mental workload was associated with the lightbar display. Eye-glance behavior revealed that when the guidance information was available through the stacked and mapping displays, subjects spent more time looking at the display. Subjective rating scales contradicted performance and physiological data; more mental workload was observed for the lightbar display. While performance and physiological measures suggest that the lightbar display induced the lowest mental workload, subjective ratings of workload contradicted these findings.