The next time you see a car fitted with a camera on a rooftop zipping by your neighborhood, be sure to take a closer look - For it may be one of the seven self-driving cars currently being tested by search engine giant, Google Inc.

The company, which has been working on this technology for over five years, first unveiled the cars in October of 2010. However, it is only at the recently held Technology, Entertainment and Design Conference in Long Beach, CA, that the company allowed non-employees to take a test drive, albeit on a closed circuit.

The self-driving cars are equipped with a number of strategically placed sensors designed to discern traffic patterns - A rotating sensor that sits on the roof constantly scans a 200 feet area around the car. A video camera affixed next to the rear-view mirror helps detect traffic lights and warns the car's computer about any moving obstacles like pedestrians and bicyclists. Four other sensors, fitted all around the car, feed the computer with information about the position of objects that are at a distance, so that car is fully informed at any given second. In addition to that, detailed maps and speed limits for every route are programmed into the database, so that the speed can be adjusted accordingly.

If that is not enough, the car can also be programmed to take on the personality of the driver - Cautious for people who are prone to yielding to other cars and aggressive for those who are likely to try zoom through.

A human driver can manually override the robot anytime he/she senses any danger like someone skipping a red light, by doing one of three things - Touching a red button placed near the steering wheel, hitting the brakes or turning the steering wheel.

The company, which has to-date fitted six Priuses and an Audi TT with their technology, says that their cars have driven autonomously for over 140,000 miles in areas ranging from the steep and windy, Lombard Street in San Francisco, to the shores of Lake Tahoe. The only accident they have ever been involved in, was when hit in the rear by another car, whilst waiting at a traffic light.

However, since the technology is still in its infancy and, it is not quite legal to whiz around in an unmanned car, the company always has a trained safety driver behind the wheels and a software engineer in the passenger seat to ensure that everything is functioning properly.

So why is the search engine getting into the car business? Because it is the company's mission to try solve large problems using technology - And by developing autonomous cars they can not only free up people's time, but more importantly, prevent traffic accidents, since research shows that most car accidents happen due to human error.

However, before you get your hopes all high, the company admits that it will take at least another decade before these cars will be allowed to zoom around driverless - But the future certainly looks bright doesn't it?

Resources:googleblog.blogspot.com, cnet.com, theweek.com