Mark Harris:

Google has built a “Matrix-style” digital simulation of the entire Californian road system in which it is testing its self-driving cars – and is lobbying the state’s regulators to certify them based on virtual rather than real driving.
 The extensive simulation – reminiscent of the virtual cities created for human captives in sci-fi blockbuster The Matrix – exists entirely inside computers at the company’s Mountain View location, and the cars have so far virtually “driven” more than 4 million miles inside it, facing challenges just like those in the real world, such as lane-weaving motorists, wobbly cyclists and unpredictable pedestrians.