Doubts over autonomy control handover

Expected congestion busting and road safety benefits of driverless cars may be undermined as a result of slow human response to the ‘handover’ process from autonomous to manual vehicle control.

So says latest research from the Atkins led VENTURER consortium which aims to understand the implications and push forward development of connected and autonomous vehicles.

The team tested the response times of 50 participants when alerted to take back control of an autonomous car. The ‘baseline’ driving behaviour of participants was recorded, followed by the length of time it took them to return to this baseline after handover.

Trials were carried out in a simulator at various speeds up to 50MPH, and in a real autonomous vehicle on the University of the West of England (UWE) Bristol campus at 20MPH.

The researchers found that it took two to three seconds for participants to take over manual controls and resume active driving in urban environments. Participants drove more slowly than the recommended speed limit for up to 55 seconds following a handover request, indicating more cautious, but not necessarily safer, driving. 

If drivers on the road replicated this behaviour the researchers claimed it might impact the flow of traffic and mitigate some of the predicated benefits of autonomous vehicles.

In addition it took typically 20-30 seconds for participants to return to their baseline manual driving behaviour after handover, and longer than this at higher speeds.

“In the time it takes for drivers to reach their baseline behaviour, the vehicle may have travelled some distance, depending on the speed,” commented UWE Bristol’s Dr Phillip Morgan.

“Designers need to proceed with caution and consider human performance under multiple driving conditions and scenarios in order to plot accurate takeover and handover time safety curves.”

Professor Graham Parkhurst of the University added that autonomous vehicles on highways may need to slow to a safe speed – lower than 70 or even 50MPH – before handover is attempted.