Abstract
The level 3 autonomous driving function allows the driver to perform non-driving-related tasks such as watching movies or reading while the system manages the driving task. However, when a difficult situation arises, the driver is requested to return to the loop of control. This switching from driver to passenger then back to driver may modify the driving paradigm, potentially causing an out-of-the-loop state. We tested the hypothesis of a linear (progressive) impact of various autonomous driving durations: the longer the level 3 autonomous function is used, the poorer the driver's takeover performance. Fifty-two participants were divided into 4 groups, each group being assigned a specific period of autonomous driving (5, 15, 45, or 60 min), followed by a takeover request with a time budget of 8.3 s. Takeover performance was assessed over two successive drives via reaction times and manual driving metrics (trajectories). The initial hypothesis (linearity) was not confirmed: there was a nonlinear relationship between autonomous driving duration and takeover performance, with one duration (15 min) appearing safer overall and mixed performance within groups. Repetition induced a major change in performance during the second drive, indicating rapid adaptation to the situation. The non-driving-related task appears critical in several respects (dynamics, content, driver interest) to proper use of level 3 automation. All this supports previous research prompting reservations about the prospect of car driving becoming like train travel.