Thursday, 13 December 2018

Lowering the drink-drive limit had no effect in Scotland

Drunk driving isn't a very popular cause, and rightly so. It is obviously wrong to risk the lives of others by driving while inebriated. By contrast, driving after consuming a small quantity of alcohol poses no threat to others and is fine, but it is this that the temperance lobby is going after. It's so much easier to hassle normal people for having a pint after work than to clamp down on the dwindling number of habitual drunk-drivers.

Always eager for an easy, feel-good headline, the Scottish government voted unanimously in favour of reducing the drink-driving limit from 80 mg of alcohol per 100 ml of blood to 50 mg of alcohol per 100 ml of blood. The change came into effect in December 2014. The rest of the UK kept it at the same level.

The new law was announced with the usual smug, patriotic, self-righteous rubbish from the politicians responsible:

Scotland's Justice Secretary Michael Matheson has predicted the lower limit will save lives.

Mr Matheson said: "Scotland is leading the way across the UK. The new limit has backing from experts, road safety campaigners and the majority of the public north and south of the border."

Amongst the "experts" were our old friends at the Sheffield Alcohol Research Group. You may remember them from their game-changing modelling of minimum pricing. Less well known is their modelling on what would happen if the drink-driving limit was reduced from 0·08 g/dL from 0·05 g/dL. Their model was limited to England and Wales but their conclusion should broadly apply to Scotland as well. It predicted that...

...lowering the legal limit would reduce fatalities by 6.4% and injuries by 1.4% in the first year after its implementation.

Evidence has steadily emerged over the last few years showing that the reduction in the limit has had absolutely no effect on road traffic accidents or fatalities. For example...

The study by Strathclyde University found that the lower limit for blood alcohol content (BAC) had not been followed by a statistically significant overall drop in road fatalities, including during the peak accident periods of night-time and weekends.

There was also little change in the death rate for young drivers aged 16-25, who are seen as one of the highest-risk groups for drink-driving.


The introduction of a lower drink-drive limit in Scotland has had virtually no impact on the rates of offending, police statistics have revealed.

None of this has made any difference to policy. Nanny state legislation is never repealed.

What is clear, however, is that the legislation has had a predictably negative effect on rural pubs. The pub trade and the Campaign for Real Ale said that it was hurting trade without bringing about any reduction in road accidents, but they were ignored. The Scottish government paid no attention and the puritans probably considered the damage to the evil booze industry to be a bonus.

Today, the reality has emerged in the Lancet of all places:

Lowering the driving BAC [blood alcohol content] limit to 0·05 g/dL from 0·08 g/dL in Scotland was not associated with a reduction in RTAs [road traffic accidents], but this change was associated with a small reduction in per-capita alcohol consumption from on-trade alcohol sales.

Note the use of the word 'but', as if the total failure of the policy is compensated by the success in reducing pub sales. For the 'public health' lobby, the destruction of pubs counts as a success. It's never really about health.

Not only does the study show no benefit from the change, the authors find that the number of road traffic accidents has increased relative to England and Wales:

...the reduction in BAC limit for drivers was not associated with a significant change in weekly RTA [road traffic accidents] rates in Scotland, after adjustment for seasonality and underlying temporal trend (model c; rate ratio [RR] 1·01, 95% CI 0·94–1·08; p=0·77; table 2).

Further, relative to England and Wales, where the reduction in BAC limit for drivers did not occur, we found no change in weekly RTA rates after this reduction in BAC limit for drivers in Scotland (model c; 1·07, 0·98–1·17; p=0·10).

Further adjustment for the driver characteristics of age, sex, and socioeconomic deprivation produced similar results, showing a significant 7% increase in weekly RTA rates in Scotland relative to England and Wales (model d; 1·07, 1·02–1·13; p=0·007).

The latter finding is based on a counter-factual and is therefore speculative but it is now beyond doubt that there have been no benefits to road safety from the Scottish government's decision to lower the drink-driving limit.

In a desperate attempt to salvage something from this pub-destroying policy, the authors suggest that the failure to reduce drink-driving accidents is due to a lack of enforcement:

One plausible explanation is that the legislative change was not suitably enforced—for example with random breath testing measures. Our findings suggest that changing the legal BAC limit for drivers in isolation does not improve RTA outcomes.

In truth, this is far from 'plausible'. The study itself shows that pub sales fell after the law came into effect, and the pub trade has been complaining about the negative effect on business almost from the outset. Both of these facts suggest that people in Scotland have been abiding by the new law. Enforcement has nothing to do with it.

A more likely explanation is that drink-driving accidents are caused by people who are heavily intoxicated, not by people who have consumed a trivial amount of alcohol. Therefore, clamping down on motorists who are not in the least bit drunk was never likely to tackle the damage done by drunk-driving.

Anyone with a bit of common sense could have told the SNP that in 2014. Instead they chose to believe some expensive guesses from the clowns at Sheffield University (not for the last time).

Will the limit be changed back? Of course not. Was the ban on alcohol discounts repealed when it was shown to have had no effect? No. Will minimum pricing be repealed if it is shown to have no effect? No.

As I have said many times, 'public health' is not a results-driven business.

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