A new EU project called Sartre will develop and test technology for vehicles that can drive themselves in long road trains on motorways. Its inventors say the technology has the potential to improve traffic flow and journey times, reduce accidents and improve fuel consumption and hence reduce CO2 emissions.

HOW IT WORKS: The truck at the head of this road train is under full manual control while the five cars behind it have locked onto its signal and are following closely to maximise the slipstream effect - without any input from their drivers.