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.
The ambition of the simulation illustrates how serious the tech company is at developing self-driving cars, an innovation that has been independently estimated as worth billions of pounds if widely implemented.
California's regulations stipulate autonomous vehicles must be tested under "controlled conditions" that mimic real-world driving as closely as possible. Usually, that has meant a private test track.
But Ron Medford, Google's safety director for the self-driving car programme, has been arguing that the computer simulation should be accepted instead. In a letter in early 2014 to California state officials, which the Guardian has obtained under freedom of information legislation, Medford wrote: "Computer simulations are actually more valuable, as they allow manufacturers to test their software under far more conditions and stresses than could possibly be achieved on a test track."
He added: "Google wants to ensure that [the regulation] is interpreted to allow manufacturers to satisfy this requirement through computer-generated simulations."
The company has also lobbied officials to change the wording of the rule to explicitly allow digital models. That, however, has been turned down. "The driving simulator is a relatively new tool - we didn't have anything like it a few years ago," Google spokeswoman Katelin Jabbari told the Guardian. "It's now a critical part of how we test and refine our software."
Google's real self-driving cars use a combination of onboard computers, stored maps, laser guidance and object recognition to determine appropriate speeds and actions to take. They operate over a limited area of about 2,000 miles of road that Google has mapped in minute detail in California - a fraction of the 172,000 miles of public roads in the state. But they have driven over that range many times: the cars have notched up a total of 700,000 miles over those 2,000 miles.
Using that data, Google has encoded how various situations unfold and how other road users are likely to behave.
"We've developed models of what a car approaching a four-way stop at high speed is likely to do, and what the various probabilities are that it will stop normally, screech to a stop or run the stop sign," said Jabbari.
"In a few hours, we can test thousands upon thousands of scenarios which in terms of driving all over again might take decades."
One of Google's self-driving cars. The tech giant is now trying to test driverless cars in the virtual world Photograph: Google