As autonomous vehicles become more prevalent in our everyday lives, we must succumb to the realities of technological deficiencies. Although a future of fully autonomous vehicles would be the pinnacle of safety and efficiency, the current reality leaves us in a transitional state requiring human interaction with autonomous systems. Therefore it is imperative to understand human-system interaction with the autonomous features in current and future technologies. To gain an improved understanding, we designed an investigational study to gain a better understanding of human performance parameters at the moment they relieve and regain control of autonomous systems. The current findings show that reaction time increases as time disengaged from the task of driving increases, regardless of cognitive engagement.

As the prevalence of autonomous vehicles onto the road increases, understanding the cognitive processes of the inevitably distracted driver is important. When engaged in a secondary task while driving, the driver’s limited supply of attentional resources is diminished, resulting in less attention available to process the unpredictable road ahead. While driving distracted causes performance to suffer across the board (Fitousi & Wenger, 2011), some individuals are more apt at multitasking than others due to a high working memory capacity (WMC). We evaluated the differences in braking reaction times (RT) according to individual difference in WMC, specifically while driving in an autonomous car simulation and engaged in a cognitively demanding task. Results showed an interaction between current level of cognitive load and an individual’s WMC where individuals who scored lower on a complex operation span task (OSPAN) experienced greater RTs compared to individuals who scored higher. Average RT during the autonomous scenario, in which OSPAN was concurrently performed, yielded a 33% increase in RT compared to baseline RT with the same OSPAN task. Additionally, sleep and length of time spent in autonomous mode influenced RT.

The assimilation of automation in commuter vehicles is rapidly increasing, as too are the concerns with these technologies. Human interaction with autonomous vehicles must be thoroughly researched to understand the quantification and qualification of interactive behaviors with these systems. We developed a study using a high-fidelity driving simulator to mimic probable breakdowns with these systems to better understand the subsequent human responses and to explore the necessary technological requirements to overcome potential problems. 30 participants engaged in a driving scenario switching between manual and autonomous vehicle control. We accounted for individual differences in braking reaction time while simultaneously engaging in a secondary cognitive task during times of autonomous vehicle control. Results show the average RT for baseline scenarios without the cognitive task was 832.1 milliseconds while the average RT for baseline scenarios with the cognitive task was 908.4 milliseconds; a 9.17% significant increase. The average RT for the autonomous scenario was 1357.0 milliseconds; a significant increase of 49.38% over the baseline scenario with the cognitive task that can be attributed to the addition of automation. We found a positive linear correlation of time spent in autonomous control and subsequent braking reaction time. Additionally, cognitive task difficulty, attention allocation, self-reported mental demand, fatigue, and heart rate affect reaction time when cued to take control of the vehicle.