Google Inc. has successfully patented its futuristic driverless car technology that allows a human driver to pass the wheel to the self-driving car.

The patent which covers "methods and devices for transitioning a mixed-mode autonom ous vehicle from a human driven mode to an autonomously driven mode" was awarded Tuesday by the U.S. Patent and Trademark Office. Google had applied for the patent in May but was only released this week.

Google's self-driving car was announced in October 2010 and even back then the car was already in advanced development. The method involves two sets of sensors: a "landing strip" or an embedded sensor in the ground that transmits information to the car and another sensor that receives the data and tells the car where it is and where it should go. The "landing strip" can transmit directions from a URL, QR code or radio link. The sensor doesn't have to be embedded in the ground; it can be a sign on a wall or lines and arrows showing where the car should be parked.

"The landing strip allows a human driving the vehicle to know acceptable parking places for the vehicle," according to the patent filing. "Additionally, the landing strip may indicate to the vehicle that it is parked in a region where it may transition into autonomous mode."

The patent seems to suggest that the car could switch from autonomous mode to user-controlled mode. Google's car can use GPS technology to orient it but if the GPS receivers don't work, the car can monitor its path and adjust its direction to the appropriate location.

The landing strip could upload new instructions to the car which will tell the car when to move or even leave the designated stopping point. Google tells a scenario where the car is used to tour Chicago's Millennium Park.

"For example, the autonomous vehicle may be used as a virtual tour guide of Millennium Park in Chicago," the patent states. "In the example embodiment, the vehicle may have an instruction to drive to the Cloud Gate (Silver Bean) sculpture at Millennium Park. When the vehicle arrives, the autonomous instruction may tell it to wait in the location for a predetermined amount of time, for example 5 minutes. The instruction may then direct the vehicle to drive to the Crown Fountain at Millennium Park and again wait for 5 minutes. Next, the instruction may tell the vehicle to drive to the Ice Rink at Millennium Park and wait for another predetermined amount of time. Finally, the vehicle instruction may tell the vehicle to return to its starting position."

Google has been testing self-driving cars for a number of years. The company had already tested self-driving cars which drove from Los Angeles to San Francisco with limited human input, before the concept was announce in October 2010.

In June, Google successfully lobbied the state of Nevada to pass laws legalizing self-driving cars for use in highways. With this patent Google could block other competitors from using the same method to switch from autonomous driving to manual driving. It seems like the future of car technology is headed for a Google-led autonomous revolution.