Self-driving cars: who's building them and how do they work?

From self-driving cars to robot lorries, autonomous vehicles are the future of road transportation. But who's in pole position, who's stuck in the pit lane and how far away is the starting grid? Autonomous vehicles are already on our roads. At the cutting edge there are self-driving cars being tested in pilot programmes, and they are proving perfectly capable of motoring alongside human drivers. But beyond robotic cars, many high-end vehicles available today are already practically capable of driving themselves either under the guise of passenger safety or driver convenience.