Autonomous vehicles: 'handover' process crucial say researchers

The Atkins-led VENTURER autonomous vehicle research project has released results from initial trials. These demonstrate significant issues to be addressed with processes of switching from autonomous to manual vehicle control.

The VENTURER trials, with partners including AXA Insurance, BAE Systems, Williams and the Universities of Bristol and the West of England (UWE Bristol) is working to develop understanding of drivers and barriers to widespread adoption of autonomous vehicles. Initial tests have set out to investigate 'takeover' time, for drivers taking back manual control, and 'handover' – the time taken for drivers to regain full, normal driving behaviour when switching frequently between manual and autonomous control in urban environments. 

While other autonomous vehicle projects are studying the effectiveness of fleets of driverless vehicles as on-demand public transport, the VENTURER project envisages privately owned autonomous vehicles that will allow the driver to take back control if necessary.  How this is done and the time it takes is critical for insurance implications. A key finding was that drivers takeover control within 2-3 seconds, but handover back to normal driver behaviour takes much longer, up to a minute or more during the highest speed test condition of 50mph.

The chair of the project, Atkins' Lee Woodcock, said: “The outcome of this research for trial one is significant and must provide food for thought as the market develops for driverless cars and how we progress through the different levels of automation.Further research must also explore interaction not just between vehicles but also with network operations and city management systems."

Dr Phillip Morgan of UWE Bristol said, “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. In the time it takes for drivers to reach their baseline behaviour, the vehicle may have travelled some distance, depending on the speed.  These initial trials show that there are some risk elements in the handover process and bigger studies with more participants may be needed to ensure there is sufficient data to build safe handover support systems.”

UWE Bristol's Professor Graham Parkhurst said the results suggest autonomous vehicles should slow to a safe speed for handover to manual control. This could have serious implications for traffic flow and the popularity and acceptance of semi-autonomous vehicles. 

"Further research is required to clarify what that safe speed is, but it would be substantially slower than the 70 mph motorway limit, and somewhat lower than the highest 50mph speed considered in our simulator trials,” he said.