Drivers don’t suddenly fall asleep without warning and they may well have already tried to fight off the ill effects of tiredness by opening the window or turning up the radio. The benefits of these efforts are short-lived and the only real cure is proper sleep.
Take regular breaks on long routes and make sure to actually rest when you take those breaks. A quick visit to the toilet and fuelling up isn’t going to allow you to recover. If you’re feeling tired drink two cups of coffee or a high-caffeine drink but remember that caffeine will only offer a short-term benefit and you are likely to feel worse when the caffeine wears off.
Peak times for fatigue related crashes are in the early hours of the morning and just after lunch.