THREE weeks tomorrow Scotland will finally fall into line with the rest of Europe and see our drink-drive limit cut to 50mg of alcohol per 100ml of blood.

The current UK-wide limit of 80mg has been in place since 1966 and will continue to be the legal limit in the rest of the UK, along with Malta. The rest of Europe already operates a 50mg or less limit in line with EU guidelines.

Policymakers hope for the kind of success already seen in countries such as Switzerland, which slashed its death rate from drink driving by more than 40 per cent between 2005 and 2008 after switching from an 80mg to a 50mg limit.

The shorthand has been to say that the new limit means motorists could be breaking the law by consuming a single pint or glass of wine, though in reality it depends on how each individual metabolises alcohol. It varies according height, weight, gender, age, type of alcohol, medication, food consumption, and activity levels - and simply "feeling sober" is no measurement. In short - as the Scottish Government campaign will tell us - it will be safer to avoid it altogether.

That is certainly a far cry from the UK's first drink driving awareness campaign which was first broadcast 50 years ago this week, before there was even any law against it or a breathalyser to test motorists at the roadside - they were not introduced until 1967.

True to its time, the advert helpfully warned motorists about the potential risks of drinking "four to six whiskies" before driving. This was an era when many motorists, especially in rural areas, would routinely drink and drive.

The advert also appealed to female viewers, urging them not to let their husbands and boyfriends drive them home from the pub with the now-cringeworthy tagline: "Don't ask a man to drink and drive".

It is impossible to say what the death toll of drink-driving was at that time because road casualties linked to alcohol have only been recorded since 1979. In that 34-year period, however, casualties across the UK have steadily decreased from 1,640 people killed and 8,300 seriously injured in 1979 to 230 fatalities and 1,200 people seriously injured by 2012, the last year for which statistics are available. According to the Scottish Government, 20 road deaths - around one in every ten each year - are caused by drink driving, lower than the UK average. The hope is the new lower limit, due to come into force on December 5, will reduce that even further.

Some campaign groups would like to see it cut again, however, to a "zero tolerance" limit of 20mg per 100ml of blood. Road safety charity Brake has launched its Not a Drop campaign with this target in mind and is calling on political parties to make it a manifesto pledge in the 2015 General Election.

This is already the standard in Sweden, Poland and Greece, with Northern Ireland due to impose a 20mg limit on newly-qualified and commercial drivers in addition to matching Scotland's 50mg limit by next year. It is difficult to see how Westminster can continue to lag behind.