For Google's self-driving cars, learning to deal with the bizarre is essential

In 700,000 miles of navigating Bay Area and other roads, Google's self-driving cars have encountered just about everything -- including an elderly woman in a motorized wheelchair flailing a broom at a duck she was chasing around the street. Apparently perplexed and taking no chances, the vehicle stopped and refused to go further. Through extensive testing covering nearly every street in Mountain View, the company's 20 or so autonomous vehicles have developed an abiding sense of caution. But Google researchers concede it will take more experience on the roads before the autos can learn to cope with every situation without becoming bewildered and shutting down, stranding passengers. When that happens now, researchers have to take the wheel and step on the gas.