What happens if the Waymo computer fails?

You buckle into the back seat of a Waymo, the doors close and there is nobody behind the wheel. For some riders, that empty driver's seat still takes a little getting used to. Then another thought creeps in. What happens if the Waymo computer doing all the driving suddenly fails?

Waymo has now given us its first detailed look at the powerful computing system hidden inside its driverless vehicles. The company describes a machine built to make decisions in milliseconds without waiting for the cloud or a remote human driver.