An anonymous reader writes Google has been testing its autonomous vehicles on U.S. roads for a while now. In fact, they're required to, by law. "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 or temporarily closed public road." It's easy enough to test a few prototypes, but whenever autonomous cars start being produced by manufacturers, it'll become a lot more complicated. Now, Google is lobbying to change that law to allow testing via computer simulation. Safety director Ron Medford said, "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." Google spokeswoman Katelin Jabbari said, "In a few hours, we can test thousands upon thousands of scenarios which in terms of driving all over again might take decades." Shee adds that simulator data can also easily provide information on how human behavior creeps into driving. "It's not just about the physics of avoiding a crash. It's also about the emotional expectation of passengers and other drivers." For example, when one of Google's computer-controlled cars is cut off, the software brakes harder than it needs to, because this makes the passengers feel safer. Critics say relying heavily on simulation data is flawed because it doesn't take into account how other cars react to the computer's driving.