Careful consideration must be given to the length of time required for passengers to be handed back control by future autonomous vehicles, researchers at the University of Southampton have urged.
A recent study at the University involving a driving simulator found that, under non- critical conditions, participants needed between 1.9 and 25.7 seconds to safely switch from automation to manual driving.
Such a large range in control transition times reflects a variety of driver behaviour and environmental conditions, commented engineers Professor Neville Stanton and Alexander Eriksson, who led the study.
The researchers observed 26 men and women engaged in simulated driving at 70MPH, both with and without a potentially distracting ‘non-driving’ secondary task. A takeover request was issued at random intervals and it was found that those engaged in a secondary task prior to a control transition took longer to respond – posing a safety hazard.
It is hoped that the findings will prove important in the development of automated vehicles. “We hope our findings can guide policymakers in setting guidelines for how much lead time a driver will need when changing in and out of automation,” commented Professor Stanton.
“The challenge for designers is accommodating the full range of response times rather than limiting parameters to mean or median transition times.”
The researchers also warned against deciding the lead time for normal non-critical control transitions based on data gathered in studies of critical situations. “Too short a lead time, for example seven seconds prior to taking control as found in some studies of critical response time, could prevent drivers from responding optimally,” explained Mr Eriksson.
“This results in a stressed transition process, whereby drivers may accidentally swerve, make sudden lane changes, or brake harshly. Such actions are acceptable in safety critical scenarios when drivers may have to avoid a crash, but could pose a hazard for other road users in non-critical situations.”