SAN FRANCISCO — In Silicon Valley, where companies big and small are at work on self-driving cars, there have been a variety of approaches, and even some false starts.

The most divergent paths may be the ones taken by Tesla, which is already selling cars that have some rudimentary self-driving functions, and Google, which is still very much in experimental mode.

Google’s initial efforts in 2010 focused on cars that would drive themselves, but with a person behind the wheel to take over at the first sign of trouble and a second technician monitoring the navigational computer.

As a general concept, Google was trying to achieve the same goal as Tesla is claiming with the Autopilot feature it has promoted with the Model S, which has hands-free technology that has come under scrutiny after a fatal accident on a Florida highway.