Should the UK lower the drink driving limit?

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One of the most frequent analyses in a toxicology lab is determination of the blood alcohol level, either from a deceased person or from a suspected case of drink driving.


This post was prompted by some reading on Scottish devolution (!).  Under power devolved in the Scotland Act 2012 the Scottish Parliament is now able to set their own drink drive limit – and they seem intent on doing so.  In the UK the current drink driving limit is 80 milligrams of alcohol per 100 millilitres of blood.  Worldwide I could only find the Cayman Islands having a higher limit (100 mg/100 mL). In Europe only 4 countries have kept their limit at 80 mg/100 mL whilst others have moved to 50 mg/100 mL (including France and Germany) whilst others are lower at 20 mg/100 mL (including Poland and Norway) .  Other countries in the world who still have a limit of 80 mg/100 mL are debating lowering (such as the US and New Zealand).  Scotland now has the power to alter their own drink drive limit whether England and Wales do or not.  In 2010 a report was prepared by the Transport Select Committee which recommended lowering the limit to 50 across the UK, but this was not supported by the Government.

So what are the stats like for the UK?

According to the last figures from the Department of Transport (2011) there were 280 fatalities resulting from drink driving accidents, 1290 people were seriously injured and more than 8 000 mildly injured.  These numbers actually show a slight increase from 2010 but they trend has been downwards for a long time, with those numbers roughly half those from 2003.  We have a generation who have been bombarded with the ‘none for the road’ type mantra and public info films and the message seems to be getting through.  However, last year there were more than 50 000 drink driving convictions proving there are still loads of people who feel they can get away with drink driving.

What good would lowering the limit do?

Projections suggest another 80-160 lives could be saved each year –  just by dropping the limit half those lives lost on the roads could be saved.  The National Institute for Health and Care Excellence (NICE) published a report estimating that 145 lives would be saved (and 3 000 fewer injuries) by dropping the limit, based on studies from European countries who have already dropped theirs.  The report indicates support for the measures from the British Medical Association, the Royal College of Physicians and the Alcohol Health Alliance UK.

With relation to effects on the body it is clear that above 50 mg/100 mL the effects start to increase rapidly in most.  The level of risk of accident rises dramatically with that.  Anecdotal evidence supports this: I have done an experiment (a highlight of my studies) where a group of us students took a breathalyser to a pub and recorded our levels over time.  By the time I got to around 50 mg/100 mL there was no way I would have wanted to get into a car to drive. I was very surprised how many drinks it took me to reach the limit.  This was supported by everyone there – our alcohol levels were lower than we estimated from our sense of intoxication.

One common thought is that one single drink would be enough to be put you above the limit if it were lower.  Have a look at this great infographic from a colleague of mine in NZ (full story here).  It clearly shows the drinks required over the two hour drinking period to reach either the 50 or 80 mg/100 mL level. Each circle represents one unit – approximately half a pint of beer.  Click to enlarge. 

There have also been concerns raised over the number of people who would be caught on the ‘morning after’ with a lower limit.  This may be true, you remove around 1 unit of alcohol per hour.  A bottle of wine has around 9 units, meaning it would take nine hours to clear a bottle from the blood of an average person. This is from the start of alcohol metabolism (usually around 30 minutes after drinking.  If you drink a whole bottle of wine over dinner, starting at 8.30 pm, the alcohol should be out of your system by around 6 am.  If you add an aperitif and a nightcap to that there is then the distinct danger of being over the limit with an early drive to work/shops and so on.


In the near future Scotland has the aim of lowering the limit to 50 mg/100 mL to be in line with the vast majority of Europe.  MSPs are also asking the UK government further devolve powers to set different limits based on a driver’s age and experience.  This is currently legislation in New Zealand where they currently have a zero tolerance limit for under 20s and 80 mg/100 mL for over 20s.  The UK Government has declined to explore the 50 mg/100 mL option and instead has the aspiration of aiming for 20 mg/ 100 mL ‘some time in the future’.


Any thoughts?  Do you think the alcohol limit should be lowered or is it more a case of enforcing the current system more effectively?


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About Dr Tom Bassindale

Dr Tom Bassindale is a forensic scientist, and the founder of We Are Forensic. He is currently the subject lead for chemistry and forensic science at Sheffield Hallam University. He's managed hundreds of forensic toxicology cases, and is an experienced court witness. He has specialist expertise in forensic toxicology and drug testing in sport. And yes... he watches CSI.