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Toyota's Pratt says human nature is big factor in autonomous-driving technology (Photo: Bongard)

Amid all the enthusiasm for driverless cars, a senior Toyota executive, speaking at the CES consumer electronics show, focused on some of the big challenges that will need to be overcome before autonomous driving can be adopted on public roads.

Gill Pratt, who heads the Toyota Research Institute (TRI), said current attempts to introduce so-called SAE Level 3 driving are already running into difficulties. "It is possible that level 3 may be as difficult to accomplish as level 4," Pratt told reporters at CES.

Level 3 lets computer systems take over the driving but expects a human driver to take over a car's controls when needed. In level 4, such intervention is no longer required, but the car can only drive fully autonomously under certain conditions or in certain environments. Level 5 doesn't require a human driver under any conditions.

Pratt, a computer scientist who is the first chief of the one-year-old TRI, said getting a driver to take over under level 2 is potentially fraught with problems because the human brain isn't always immediately ready for the job. "Considerable research shows that the longer a driver is disengaged from the task of driving, the longer it takes to re-orient."

People also tend to have too much trust in current automated-driving technology, the Toyota executive said. "When someone over-trusts a level 2 system's capabilities, they may mentally disconnect their attention from the driving environment," he said.

Fully autonomous driving isn't likely to happen anytime soon, Pratt said. "None of us in the automobile or IT industries are close to achieving level 5 autonomy," he said. "It will take many years of machine learning and many more miles than anyone has logged of both simulated and real world testing to achieve the perfection required for level 5 autonomy."

Pratt said the push for driverless cars also needs to deal with the different ways people look at human and machine performance. "Society tolerates a lot of human error," he said. "But we expect machines to be much better."

Because of this, driverless-car technology will be held to a much higher standard than human drivers have ever needed to achieve. Said Pratt: "Historically, humans have shown nearly zero-tolerance for injury or death caused by flaws in a machine."

-By Arjen Bongard