An important consideration for the ability of human drivers to manage automated driving is the amount of time they have available to reengage in the driving task. Therefore, as part of the HADRIAN project, the German Federal Highway Institute (BASt) performed a literature review to approximate how much time drivers need to actively exercise vehicle motion control after having engaged in a secondary task during an active SAE Level 2 phase (so called re-engagement time). Based on 33 mean re-engagement times obtained from 16 publications, a time budget of 5 seconds for re-engagement was found to cover most of the mean re-engagement time values found in the literature.

BASt also performed a Wizard-of-Oz study in a real driving setting with ADL 3 functionality on a test track to measure takeover times from natural non-driving related activities (playing Tetris, reading & typing, watching a documentary film). Half of the participants experienced rides in the dark, the other half at daytime. The study indicates that takeover times both at daytime and in the dark, and after engagement in natural non-driving related activities during SAE Level 3 automated driving were below 15 sec. Therefore, these times are used in the HADRIAN project as threshold for the maximum take-over times from automated driving at Level 2 and 3. The studies are also being described in detail in a forthcoming publication.