The main factors that happen when you drink is that it slows down your reaction time, it impairs your judgement, it can mean that your co-ordination is poor, you may become over-confident, you may be drowsy or sleepy, more likely to nod off or fall asleep at the wheel.

If people are drinking, the thing about .05 is that it can be hard for people to judge when they have reached .05 because it depends a lot on your susceptibility and the variabilities of what you’ve been drinking and what your body weight is and when you last ate and all that sort of thing is going to influence when your blood alcohol reading or concentration is actually at .05 and a lot of people don’t realise but your blood alcohol content can keep on rising up to two hours after you’ve finished drinking. It’s hard for people to estimate exactly where the limit is and when they’ve reached it. And even though there’s more and more portable breathalysers around, like, in pubs and stuff, if they haven’t been calibrated lately then they might give you a false reading.

So people really just have to be aware that when they have a drink that they could still be intoxicated when they leave, even if they think that they’re still under the limit—that they might not be.