The UK’s Venturer autonomous vehicle (AV) project consortium has published the results of its first trials that took place in the summer of 2016, which focused on the ‘handover/takeover’ period when transitioning between automated and manual driving modes.
The trials took place at Bristol Robotics Laboratory (BRL), and on roads at the University of the West of England (UWE) campus, using the UWE driving simulator and the BAE Systems’ Wildcat AV. The Venturer project’s first trials set out to investigate two scenarios when switching frequently between automated and manual driving modes within urban and extra-urban settings: ‘takeover’ the time taken to reengage with vehicle controls; and ‘handover’ the time taken to regain a baseline/normal level of driving behavior and performance. The transition process is important from a legal and insurance perspective, as it represents a meaningful risk to insurers, and understanding who is in control of a vehicle has liability implications.
For the trials, 50 participants were tested in a simulator and/or in the AV on roads on at speeds of 20, 30, 40 and 50mph (32, 48, 64, and 80km/h) in the simulator and 20mph (32km/h) in the AV. Baseline driving behavior of participants was also tested, and the time it took them to return to this baseline following handover.
A key finding was that it took 2-3 seconds for participants to takeover manual controls and resume active driving after short periods of autonomous driving in urban environments. Participants also drove more slowly than the recommended speed limit for up to 55 seconds following a handover request.
In addition, participants returned to their baseline manual driving behavior after handover within 10-20 seconds, with most measures stabilizing after 20-30 seconds. However, this was not the case within the highest speed simulator condition, where stabilization did not seem to occur on most measures within the 55 second handover period. The trial also clearly demonstrated that there were no major differences between behavior in the simulator and Wildcat platforms, validating the future use of simulators for the development of AVs.
“The results of this trial have been very useful as we consider the issues that the handover process raises for insurers as they come to market,” noted David Williams from consortium member AXA Insurance. “Although some motor manufacturers have said they will skip SAE Level 3, some are progressing with vehicles that will require the driver to take back control of the vehicle.”