MOUNTAIN VIEW, Calif. — Google is the latest company to take a shot at inventing a car that drives itself.

It’s a long way from being mass produced but after spending about $10 million in R&D, Google last week dispatched a Prius equipped with sensors, GPS, video cameras, radar and laser range finders (among other innovations) to wind its way through several California streets, with someone at the controls.

Rest assured, a human behind sat behind the wheel, ready to over-ride the technology. And he did, twice, once when a bicyclist ran a red light and the other time when the car in front stopped short. But researchers maintain that the driver didn’t really need to act; the robot/car would have responded satisfactorily anyway.

According to the New York Times, the Prius not only found its way through a maze of neighborhoods, it merged on to Highway 101 and kept up with the fast-moving traffic through, appropriately enough, Silicon Valley. The test drive lasted about a half hour.

The car stayed at within the posted speed limit. (Google has every speed limit on the road in its database and you already know about Google’s mapping capabilities.)

And when it approached intersections, the car told the human at the wheel what it was doing, as in, “approaching a crosswalk” presumably to re-assure him that everything was under control.

The driver, rather, the guy behind the wheel, was a Carnegie Mellon University scientist named Christopher Urmson. All he had to do to over-ride the system was hit a red button near his right hand, touch the brake pedal or turn the steering wheel.

The inventor of the car is one Sebastian Thrun, a 43-year-old director of the Stanford Artificial Intelligence Laboratory, and a co-inventor of Google’s clever Street View mapping service.

Five years ago, Thrun won a Grand Challenge put out by the American Defense Advanced Research Projects Agency (DARPA) when he and a team created Stanley the Robot Car, a VW Touareg that completed a 100-plus-mile off-road obstacle course through the California’s Southwest Desert. Stanley is now in the Smithsonian Museum.

Top engineers have been working on perfecting the unmanned vehicle for decades — and not just small cars.

Anyone who watches the Discovery Channel might have seen big unmanned trucks at the annual DARPA challenge, which began years ago on a 132-mile course in the desert and has since expanded to prove you can drive through an urban area without a driver.

Oshkosh’s TerraMax, for example, is a completely autonomous 10-wheel tractor-trailer, requiring no driver and no remote control, powered by drive-by-wire technology.

For more on far-out future truck and vehicle technology, check out Truck Trek, here.