Asleep at the wheel (kind of)

Who, what, why: What is a micro-sleep?
This sudden head jerk is how people commonly know they’ve had a micro-sleep as the brain doesn’t remember such short naps. “Sleep has to last beyond a minute or two for your brain to remember it,” says Prof Horne, who studied driver tiredness for 10 years. “With micro-sleep, you are just left with a feeling of not knowing if you are coming or going.”