Heart Rate Variability in Response to Task Automation in Agricultural Semi-Autonomous Vehicles

The goal of this study was to assess the sensitivity of the heart rate variability measure to variations in task difficulty and drivers’ mental workload in agricultural semi-autonomous vehicles. 30 young participants with at least one year of tractor driving experience performed steering and implement control and monitoring tasks in a simulator study. Experiments were conducted using the tractor driving simulator (TDS) located in the Agricultural Ergonomics Laboratory at the University of Manitoba. Five levels of automation support from low to high were defined for the implement control and monitoring task. One-half of the participants performed a manual steering task while the other half drove the TDS in automatic steering mode, which only required them to monitor a mapping system and supervise the computer that was performing the steering task. A heart rate monitor was used to record the participants’ heart rate. Time and frequency domain parameters of heart rate were analyzed. Some of the time and frequency domain parameters showed some sensitivity to workload variations, however, inconsistencies were observed in the results. The widely used HRV parameter, 0.1 Hz component of HRV, was not sensitive enough to differentiate mental workload levels when the drivers were involved in the task-loop.