If you find yourself yawning at the wheel, sit up and pay attention because even the briefest microsleep can cause a fatal crash, and hundreds of people die this way every year. The term microsleep refers to very short periods of sleep that can be measured in seconds, rather than minutes or hours, sleep experts say. Closing your eyes for just two seconds could leave you driving blind for 56 metres if you are moving at 100 km/h, says German safety inspection agency TÜV. Watch out for the key warning signs, say if your eyes are drifting, you startle suddenly and your movements are jerky, or your…