Leading article: Testing the limits

There will be no move to toughen up Britain's laws on drinking alcohol before driving, the Conservatives stated before the election. But we do not have a Conservative government; we have a coalition, and the Liberal Democrats have backed the idea of reducing the permissible amount of alcohol allowed in the blood of drivers from 80mg of alcohol per 100ml of blood to 50mg – as was recommended by yesterday's review of the drink-drive laws by Sir Peter North. Such a change, he said, could save 168 lives – about 7 per cent of UK road deaths – in a year.

Sir Peter makes some persuasive arguments. No one should be in command of a ton of fast-moving metal if their judgement is seriously impaired by drink. Yet society must weigh against that the social impact of removing from the vast majority of drivers the ability to legally enjoy a very modest amount of alcohol on a social occasion.

Finding the right balance is not as easy as it sounds. The evidence from Switzerland, where the law was tightened from 80mg to 50mg in 2005, is that the number of deaths was almost halved. But France suggests that legal blood limits do not tell the whole story; the limit there is already 50mg and yet the proportion of road deaths attributable to alcohol (27 per cent) is higher than the number in England (18 per cent) where more alcohol is permitted. There are other considerations. Increasing the chances of being caught may be more effective than lowering the legal levels. A quarter of drink drivers are young men aged between 17 and 24 and the majority are men under the age of 30. There may be other ways of targeting such groups.

To lower the level in the UK to 50mg, and maintain the law requiring a 12-month ban on drink-drivers, would make UK laws the toughest in Europe. Add in Sir Peter's suggestion that drivers who breathalyse over the limit should no longer be allowed to demand a blood test in confirmation – on the grounds that breathalysers are today more accurate than when they were first introduced – and the UK law would become draconian.

The Government should give serious consideration to lowering the permitted level of alcohol but it is by no means clear that it should go as far as Sir Peter suggests. The law may need to be tightened in some areas, but legislators should guard against an over-correction, which would impinge too much on the modest freedoms of the law-abiding majority.