Drink Driving

I don't think these calculations are correct. I was speaking to a cousin who is a policeman a few weeks back and he said you can drink 5 pints over a 5 hour period and pass a breathalyser test afterwards. I was surprised by those numbers but some googling backed it up. If you are failing in the morning you've had 20 units. It takes about an hour to metabolise 1 unit and there's about 2 units in a pint of standard strength beer so your 1st pint is gone by the time you are starting your 3rd, 2.5 gone by the time you finish your 5th which is about 2.5 units of alcohol left in your system which is about the limit. People forget how time affects things. Most people drink quicker than that and if you have 2 pints in an hour you can have more in your system than someone drinking slowly over 5 hours so that is where the confusion comes from.

Personally I will never have more than 2 even if I'm out all night and I'm quite happy to drink non-alcoholic beer or soft drinks. I have definitely had mornings after where I had been drinking heavily into the middle of the night where I was probably worse so it's impossible to say whether I've ever been over the limit the next morning. My guess would be I probably have but I try to give myself plenty of time before driving on a morning when I can. I'm too sensible to drink that heavily these days though.
If you drink 4% lager your policeman friend is almost correct, but not quite, needs to be careful who he gives advice to and definitely doesn't understand the sums. The main problem being the first assumption that most beer is 2 Unit per pint.

To work out units it is

Alc Vol. * Volume (ml) / 1000.

The limit for a man is 5 Units. For a woman it is 3 Units.

You metabolise 1 unit per hour from the time you start drinking. (Actually 30 mins after if you want to be really precise).

So 5 pints of 4% beer

4% * 568ml / 1000 = 2.272 Units

5 Pints = 11.4 Units.

So you needs to metabolise 6.4 units to be safe. 6.4 hours from the time you start drinking.


If you drink 5% beer each pint is 2.84 units. Which totals 14.2 Units.

This means you need to wait 9.2 hours from the time you start drinking.

Unbelievable how much difference that 1% makes.


Believe me I spent 3 full days going over these calculations a few years ago and they have stuck with me. If I know I'm going to be driving the morning after drinking, I stick to 4% beer. As you can see from the above, it makes a massive difference to your recovery times. Also remember, although these are "worst case" recovery rates, they are also only taking you to the absolute limit. Ideally you want to be calculating to zero, rather than the limit.
 
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I don't think these calculations are correct. I was speaking to a cousin who is a policeman a few weeks back and he said you can drink 5 pints over a 5 hour period and pass a breathalyser test afterwards. I was surprised by those numbers but some googling backed it up. If you are failing in the morning you've had 20 units. It takes about an hour to metabolise 1 unit and there's about 2 units in a pint of standard strength beer so your 1st pint is gone by the time you are starting your 3rd, 2.5 gone by the time you finish your 5th which is about 2.5 units of alcohol left in your system which is about the limit. People forget how time affects things. Most people drink quicker than that and if you have 2 pints in an hour you can have more in your system than someone drinking slowly over 5 hours so that is where the confusion comes from.

Personally I will never have more than 2 even if I'm out all night and I'm quite happy to drink non-alcoholic beer or soft drinks. I have definitely had mornings after where I had been drinking heavily into the middle of the night where I was probably worse so it's impossible to say whether I've ever been over the limit the next morning. My guess would be I probably have but I try to give myself plenty of time before driving on a morning when I can. I'm too sensible to drink that heavily these days though.
The simple fact is that the amount you 'can' legally drink has many variables including your own physical make up, your diet and context ie you could be under one day and over another after drinking exactly the same amount, over the same time period.

Suggesting you can drink X amount and be OK is a recipe for getting banned, or worse.
 
If you are failing in the morning you've had 20 units
That's a very broad statement. It depends when you start drinking and depends what you consider the morning...

If you start drinking at 6pm and drink 20 units and get in a car at 9am, you are right on the limit.
If you start drinking at 8pm and drink 20 units and get in the car at 6am, you will be twice the limit.

This also assumes you've calculated your units correctly, and not used 2 units per pint. As explained in the post above, if you've had 10 pints, you've likely had more than 20 units. 20 units is more like 7-9 pints depending on the strength.
 
I feel I must stress that my cousin wasn't advising it, it was just general conversation because the topic of drink driving had come up, think it was around the World cup when the campaign was on. Someone mentioned that 2 pints would be fine and someone else said 3. I mentioned the spoof 5 and drive adverts and he said it's not as far off as you think and just explained how it depends on what you are drinking and how long it takes you to drink them. He definitely wasn't recommending it.

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To make it simple, could it not be zero tolerance?
That doesn't really help, people still need to understand recovery times and how to calculate the amount of units you have drank.

All you are doing is increasing that recovery time. Unless there is data that shows there is a significant increased risk of accident when people driving under the current limit, I don't see the benefit.

The problem is, people use the limit incorrectly. They see it as "what can I get away with drinking", rather than a buffer. It's really there so you aren't prosecuting people with very little alcohol in their system.
 
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That doesn't really help, people still need to understand recovery times and all you are doing is increasing that time.
Zero tolerance works well in Dubai - If you have alcohol in your system and you are involved in a bump, you are probably going to jail.
Everybody understands this and goes by Taxi.
 
Zero tolerance works well in Dubai - you have alcohol in your system. If you are involved in a bump, you are probably going to jail.
Everybody understands this and goes by Taxi.
Sorry Wiseman, expanded on my post to explain my point better. Agree it potentially prevents people driving directly after drinking but it would increase a mans recovery time by 5 hours the morning after!
 
Sorry Wiseman, expanded on my post to explain my point better. Agree it potentially prevents people driving directly after drinking but it would increase a mans recovery time by 5 hours the morning after!
Girl I worked with in Dubai many years ago had been drinking red wine in garden.

Later in the day she went to the local shop to pick up water. On the way, a local lady driving on the phone, drove into the back of my friend.

Cops came, breathalysed my friend and found alcohol (not massive amount) in her system.

She was in prison for 3 weeks, her car impounded but the worst bit was that the local lady kicked up a huge stink that her Mercedes was damaged way beyond a dent in the bumper. She got quotes from garage for AED 65,000 (£10k approx) which my friend had to pay....on top of a fine.

Not worth it but at least the law is clear.
 
The simple fact is that the amount you 'can' legally drink has many variables including your own physical make up, your diet and context ie you could be under one day and over another after drinking exactly the same amount, over the same time period.

Suggesting you can drink X amount and be OK is a recipe for getting banned, or worse.
and any medication your on, some changes your metabolism which would also mean its in your system even longer.
 
Girl I worked with in Dubai many years ago had been drinking red wine in garden.

Later in the day she went to the local shop to pick up water. On the way, a local lady driving on the phone, drove into the back of my friend.

Cops came, breathalysed my friend and found alcohol (not massive amount) in her system.

She was in prison for 3 weeks, her car impounded but the worst bit was that the local lady kicked up a huge stink that her Mercedes was damaged way beyond a dent in the bumper. She got quotes from garage for AED 65,000 (£10k approx) which my friend had to pay....on top of a fine.

Not worth it but at least the law is clear.
But that is just stupid. If she wasn't driving dangerously and she was only in an accident because someone else caused an accident then why should she have had to go to prison and be fined so heavily. I'm not sure the draconian laws that some of the middle east have in place i something to aspire to.

I assume the limit we have is low enough that it is well within the safe zone. Zero tolerance is too strict.
 
The simple fact is that the amount you 'can' legally drink has many variables including your own physical make up, your diet and context ie you could be under one day and over another after drinking exactly the same amount, over the same time period.

Suggesting you can drink X amount and be OK is a recipe for getting banned, or worse.
Yes, absolutely right. It is absolutely impossible to say that you are safe to drive after 1 pint, or 2 pints, or any amount. There are so many variables in the equation that it's impossible to be certain.

Even between individuals of roughly the same size and build, one may pass a breathalyser, or blood test after two pints of beer and the other fail after one pint of the same beer. Other factors include whether you have eaten while drinking. You are more likely to pass breathalyser or blood tests if you have had a meal. Factors like the length of time since your first and last drink, what you are drinking, how often and how much you regularly drink, and your personal fitness levels all impact the results.
 
But that is just stupid
she was stupid for having a drink and later driving
If she wasn't driving dangerously and she was only in an accident because someone else caused an accident then why should she have had to go to prison and be fined so heavily. I'm not sure the draconian laws that some of the middle east have in place i something to aspire to.
it's the law. like it or lump it
I assume the limit we have is low enough that it is well within the safe zone. Zero tolerance is too strict.
i disagree. If it costs somebody injury or their life, it's not too strict
 
Yes, absolutely right. It is absolutely impossible to say that you are safe to drive after 1 pint, or 2 pints, or any amount. There are so many variables in the equation that it's impossible to be certain.

Even between individuals of roughly the same size and build, one may pass a breathalyser, or blood test after two pints of beer and the other fail after one pint of the same beer. Other factors include whether you have eaten while drinking. You are more likely to pass breathalyser or blood tests if you have had a meal. Factors like the length of time since your first and last drink, what you are drinking, how often and how much you regularly drink, and your personal fitness levels all impact the results

All true but there needs to be some sort of guidance so people have something to work off. Otherwise if you do have two or three pints, how would you know when you are safe? 3 hours later? 13 hours later? 3 days later?

The above comes with cavaet that it's not an exact science but is more of a worst case scenario. Many people would recover quicker, but if you worked on that guidance you could be confident you were being sensible. Alternatively buy yourself a breathalyser.
 
A few years back, France tried to introduce a law where you had to have a personal breathalyser kit in your car at all times.

Don't know if it was followed through - maybe @pierrequiroule or one of our other French residents can advise ?
 
Yup - one of the most shameful things I have done.
Quite a few times until I was around 25

Whilst I’m cleansing my soul…..
Shameful episode of Shoplifting from the age of 7 to 16
Shamefully engaged on racist chants until I was about 20 (over 40 years ago)
 
A few years back, France tried to introduce a law where you had to have a personal breathalyser kit in your car at all times.

Don't know if it was followed through - maybe @pierrequiroule or one of our other French residents can advise ?

The law proved ineffective so was finally scrapped in 2020. The kits themselves can are readily available for a couple of euros, usually in the alcohol aisles of supermarkets.

I'll sometimes use them, but know my body well enough after 70+ years, so a couple of glasses of red at the beginning of a family meal that might go on for 5 hours is always OK. I've been tested 4 times in France, the last time on the way home from the Reveillon meal this Christmas, and I've never been positive.
 
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