Research compiled by autonomous vehicle consortium Venturer found a two-second lag between when a car switches from autonomous driving to the driver being back in control.
Therefore, if a car is moving at 50mph it will have covered 45 metres before the driver has fully taken control.
Venturer says autonomous cars could be made safer by prohibiting drivers from activities like reading, sleeping, watching TV or using phones, as it would increase their reaction time in case of an emergency.
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Sarah Sharples – Professor of Human Factors at the University of Nottingham and Associate Faculty Pro-Vice-Chancellor for Research and Knowledge Exchange – said: "It is therefore important to understand the implications of increased autonomy on the capability of humans to maintain vigilance and attention in order to be able to respond to an emergency situation.
“It may also be necessary for the rollout of highly autonomous vehicles to be accompanied with the advice – or even law – that in some or all circumstances the driver must maintain attention to the driver situation and that other activities should be minimised or avoided.”
The news follows calls for autonomous car drivers to undertake a special driving test to receive a new licence before getting behind the wheel.
Professor Natasha Merat from the Institute for Transport Studies also said drivers should be trained to take back control of the vehicles safely and quickly.
Chancellor Philip Hammond previously discussed plans to have self-driving vehicles on the roads by 2021.
In his Autumn Budget speech in November, Mr Hammond said: “We support Government’s measures to make the UK one of the best places in the world to develop, test and sell connected and autonomous vehicles.
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“These vehicles will transform our roads and society, dramatically reducing accidents and saving thousands of lives every year, while adding billions of pounds to the economy.
“We look forward to continuing industry’s collaboration with government to ensure the UK can be among the first to grasp the benefits of this exciting new technology.”
