More than three decades after it first aired, my favourite description for the actual effect of alcohol on humans is still this:
"Pub. Ah, yes, a meeting place where people attempt to achieve advanced states of mental incompetence by the repeated consumption of fermented vegetable drinks."
It was said by the android character known as Kryten on the Timeslides episode of Red Dwarf, and it is funny because there is a definite truth to that statement.
Perhaps another way to think about it is the effect of beer goggles. The entire premise behind that is the more alcohol you drink, the better other people look. And this occurs because your good judgement gets less good the more advanced your fermentation-induced mental incompetence becomes.
Your inhibitions also go down, but so do your motor skills, reaction times, and ability to clearly perceive the world immediately around you (which is hard enough to do even when you're completely alert and sober).
It makes sense then that being under the influence of alcohol, or any other substance that could impair your abilities for that matter, is not tolerated on the roads.
In July 1976 Victoria became the first part of Australia to use random breath testing (RBT) as a means of enforcement.
For most drivers in Australia these days the blood-alcohol limit is 0.05 per cent, although for young or novice drivers in many jurisdictions, and often for working drivers too, the limit is either zero or 0.02 per cent (which is also basically none).
When they marked the 40th anniversary of the introduction of RBTs in 2016, Victoria's Transport Accident Commission (TAC) said "The proportion of motorists killed with a blood alcohol level of more than .05 has dropped dramatically over this time - from 49 per cent in 1977 to 15 per cent in 2014."
Occasionally there are debates around changing the limit, and not all states went for 0.05 straight away. While some countries still have higher limits, others have 0.02 or zero across the board. Japan and Sweden both reported fewer alcohol-related road incidents after lowering their respective limits more than a decade ago.
Meanwhile, the actual quantity of alcohol you can consume and then return to being sober over a set period of time varies a little per person, mainly because we're all a different size. As a guide though the standard drink, which is 10 grams of alcohol, is approximately what your body can process in an hour. This is why some people who get way too incompetent may still not be legal to drive the next morning.
In addition to RBTs, in recent years it has become more common to also test for the influence of other substances.
Transport for NSW says: "Our research shows that the presence of illegal drugs is involved in around the same number of fatal crashes as drink driving."
Implemented in a similar roadside method, "mobile drug testing (MDT) detects the presence of four common illegal drugs: ecstasy, cannabis, cocaine and methamphetamine (including speed and ice)."
The solution for you, apart from abstinence, is to ensure you do not have to drive anyone anywhere while under the influence of anything, including medications that are known to impair your capacity. So just plan ahead and either use another form of transport or have somewhere safe to fully sleep it off (and don't forget that one standard drink per hour estimation).