Why has Google built a fleet of driverless cars?

Google has a bit of a reputation for investing in bizarre projects (bicycle-powered commuter monorail, anyone?) but its latest announcement is the strangest yet. The company has revealed a fleet of driverless cars which have already covered 140,000 miles.

In a Google blog post that had readers checking it wasn't April 1, engineer Sebastian Thrun said the company hoped the technology could reduce road traffic and slash the number of car crashes.

In tests, the "automated" vehicles always travel with a driver behind the wheel, ready to take over from the software if there is any problem. Police are always notified in advance and the vehicles follow a pre-planned route.

Apparently the only accident so far has been when one of the cars was rear-ended at a set of traffic lights. How the insurance companies handled that one is not revealed.

Thrun says the robocars use video cameras, radar sensors and a laser range finder to 'see' other traffic. They navigate using Google's detailed mapping.

On test in California, the cars have crossed the iconic Golden Gate Bridge, driven round Lake Tahoe and navigated the Pacific Coast Highway. But the trips weren't just a joyride: Thrun says Google is deadly serious about the project.

"According to the World Health Organisation, more than 1.2m lives are lost every year in road traffic accidents," he writes. "We believe our technology has the potential to cut that number, perhaps by as much as half.

"We're also confident that self-driving cars will transform car sharing, significantly reducing car usage, as well as help create the new 'highway trains of tomorrow'."

Highway trains are not a new concept – it has been posited for years that in the future cars could be computer controlled to drive in tight convoys at high speeds, preventing accidents and improving fuel economy.

But why is a search engine company trying to save the world by developing a fleet of autonomous cars? Writing on BusinessInsider.com before the automated car project was made public, Jay Yarrow suggested one theory for Google's habit of investing in strange projects.

Noting that Google doesn't spend much money on traditional advertising, Yarrow observed: "Maybe funding quirky projects like windmills and beekeeping is Google's way of defining its brand."

One hundred and forty thousand miles in a fleet of intelligent cars seems like a lot of effort for a publicity stunt. Perhaps it's all an elaborate way to avoid speeding tickets, a high-tech version of the old 'someone else was driving' dodge. ·