Don't drive when you're tired, the same way you don't drive when you're drunk. Stop driving when you're tired, and take a break. Even if it's a nuisance and you want to get there quickly.

With all the focus on drinking and driving there seems to be a tendency to shrug off all the other things that can be every bit as dangerous - driving when tired, driving when you haven't eaten and your blood sugar is low, driving when you are quarrelling, driving without switching off your mobile phone...