Google self-driving cars are shown outside the Computer History Museum in Mountain View, Calif., in May 2014. Eric Risberg/AP hide caption

Self-driving Uber vehicles are lined up to take journalists on rides during a media preview at the company's Advanced Technologies Center in Pittsburgh earlier this month. Gene J. Puskar/AP hide caption

While other automakers are working on a gradual progression toward more automation in cars, Google has its eyes on a fully automated self-driving car. Bloomberg via Getty Images hide caption

A member of the media tests a Tesla Motors Model S car with an Autopilot system. Regulators and manufacturers are debating whether self-driving cars should have a licensed driver inside as a safety precaution. Bloomberg/Bloomberg via Getty Images hide caption

This Hyundai MOBIS "i-Cockpit Car" simulator let people experience autonomous driving mode at the 2016 technology show CES in Las Vegas. Alex Wong/Getty Images hide caption

There was a lot of excitement in 2012, when the Hiriko car was unveiled at this event at European Union headquarters in Brussels. At the time, the then-president of the European Commission, Jose Manuel Barroso, hailed the car as a trans-Atlantic "exchange between the world of science and the world of business." Zhou Lei/Xinhua/Landov hide caption

New autopilot features are demonstrated in a Tesla Model S during a Tesla event in Palo Alto, Calif., Wednesday. Beck Diefenbach/Reuters/Landov hide caption

A pedestrian crosses in front of a vehicle as part of a demonstration at Mcity on July 20, on the University of Michigan campus in Ann Arbor, Mich. Paul Sancya/AP hide caption

Google X is building a few hundred self-driving cars that have no steering wheel, accelerator pedal or brake pedal. Google hide caption

Car companies are picking up automobile concepts such as this Lexus SL 600 Integrated Safety driverless research vehicle, shown at the Consumer Electronics Show in early January in Las Vegas. Julie Jacobson/AP hide caption