Justin Pritchard

Computer-driven cars have been testing their skills on California roads for more than four years — but until now, the Department of Motor Vehicles wasn’t sure just how many were rolling around.
 That changed Tuesday, when the agency issued testing permits that allowed three companies to dispatch 29 vehicles onto freeways and into neighborhoods — with a human behind the wheel in case the onboard computers make a bad decision.
 These may be the cars of the future, but for now they represent a tiny fraction of California’s approximately 32 million registered vehicles.