Dearth of data making evaluation of driverless cars in America a tough job

Washington

PRESIDENT Barack Obama says that automated vehicles could cut the yearly death toll on US roads by tens of thousands. His highway safety chief talks about "a world where we could potentially prevent or mitigate 19 of every 20 crashes on the road". Uber says self-driving cars "can help save millions of lives" worldwide.

Their message is clear: Robots will be better drivers than we are. But despite the excitement and the hype, top engineers and federal regulators face a basic problem. They're still struggling with exactly how to compare man (or woman) with machine.