Five minutes after being ordered on an app, a taxi arrives outside a small McDonald’s on the edge of Shanghai. There is no welcome from a driver, because there is no driver. After entering a pin code into a panel on the rear door and jumping into the back seat, a disembodied voice from a speaker gives an instruction to put on seatbelts. The car then indicates and swings itself into the slipstream of traffic. This could be a scene from a science-fiction film, but it has become reality in 20 citie...