Possible reduction in the blood-alcohol limit for driving?

This came in today:

‘Such a serious issue is always going to be handicapped by emotive language, when it should be more evidence based and the rights of people in a free society to choose the way they behave, but be safe and acceptable to the majority of others.

As you will read, The Alliance of British Drivers (ABD) supports retention of the current blood-alcohol limit of 80 mg of alcohol per 100 ml of blood. The ABD believes that the present limit is the best compromise between deterring irresponsible behaviour and penalising drivers who present a very low risk.

There is a general acceptance that most accidents involving drinking drivers occurred at blood-alcohol concentrations (BAC) above the current limit, often by a considerable margin. The logical response, therefore, should be to concentrate on better enforcement of the current law rather than changing it.

This appears to be a view that a reduction would change perceptions of what is socially acceptable, rather than confidence that a lower limit would significantly reduce casualties. It is also claimed that public opinion would support such a change. The ABD believes, however, that motoring laws should be based on sound science, not opinion polls (which are in any case subject to the way questions are asked) or attempts at social engineering.

The above study was conducted in Grand Rapids, Michigan, USA and results published in 1964, It is often referred to as the Borkenstein trial, as he was the lead author.  It showed very little difference in impairment from zero to around 80mg/100ml, which then rose slowly to 90mg, after which it took off exponentially. 

This was the evidence that was used to impose the current limit. Based on the curve shown, where would you (or indeed any other rational person) have set the BAC limit?

There have been no radical changes in basic human physiology since this work was done. If it’s not broken, why do some people see a need to mend it, other than for the usual negative anti-car rhetoric?

The Borkenstein study also said “A drinker is more out of commission when the blood alcohol level is climbing than when it is falling … As the blood alcohol level drops in the elimination phase, the individual, when similarly tested, will be able to function better with the same blood alcohol content.”

Claims that drivers in the 50-80mg range are several times more likely to be involved in an accident than at zero BAC are probably based on a study which clearly started with the conclusions it wanted to draw and worked backwards to see how they could be achieved.

The North Review quotes the effects of lowering BAC limits in other countries in terms of casualty reduction. Many of those countries, however, previously had much higher levels of drunk driving than the UK, due to an absence of UK levels of enforcement and publicity. They were simply catching up with the social changes that had already happened here.

Also, it must not be assumed that a cut in the drink-drive limit would just lead to a reduction in the amount of alcohol consumed by drivers, while everything else would remain unchanged.

The likelihood is that some people would decide not to go out at all if there were a more restrictive limit and they had no alternative to driving. This could lead to reductions in traffic levels during ‘drinking hours’, with the result that there could be a fall in accidents, not because of less drink-driving, but because of less driving overall, hence less exposure to risk.

No doubt this would be hailed as a ‘success’ for the lower limit, but it would be at the cost of restricting leisure activities and less custom for certain businesses, especially rural public houses, which already are closing at a disturbing rate. A reduction in the legal limit would not be cost-free.

Testing a driver’s alcohol content is easy way to justify an accident, but does that cloud the real cause of any accident?

One thought on “Possible reduction in the blood-alcohol limit for driving?”

  1. On BBC’s Trust Me I’m a Doctor it said the original evidence behind the 80mg/100mL limit was that the serious accident rate doubled at that level.
    One of the persons who set this limit in the UK said new evidence shows the lethal accident rate is about 13 times so the limit should be cut.
    This Borkenstein study was never mentioned. Going by the BBC, this is not how the UK limit was arrived at. It was a UK committee.

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