There is a rule of thumb that says a normal healthy adult, who is well rested, well nourished, emotionally stable, not on any medication, with a normal body-fat content, who is not dehydrated, has not imbibed alcohol the previous day, has a normally functioning liver and kidneys, drinking at a normal pace, etc, etc. has the ability to metabolise a single unit of beverage alcohol per hour on a given day (the hour starts when the last of the drink is taken). On a different day with any of the variables changed, that ability may change, upwards or downwards.
Even if all of the metabolites that indicate the presence and level of alcohol in a person's blood-stream and therefore brain have gone, post-bender, there are other issues to be considered such as :
- Level of tiredness
- Dehydration
- Ability to concentrate
- Emotional state (anxiety, worry, regret, anger, etc.)
- Physical state (sweats, shakes, headache, dodgy tummy, etc.)
all of which may effect a person's ability to drive, cycle, roller-skate or maybe even walk safely.