Scotland has lowered its drink-driving limit. The legal alcohol limit has been reduced from 80mg of alcohol to 50mg in every 100ml of blood.
It equates, roughly, to a reduction in permissible alcohol from two pints of standard strength beer to one pint, or from one-and-a-half glasses of wine to one glass.
However, the way in which a person processes alcohol varies according to the individual and a range of circumstances.
Therefore, people travelling in Scotland are being urged not to drink any alcohol at all before getting behind the wheel.
In England and Wales, the alcohol limit for drivers is still 80mg of alcohol per 100ml of blood.
Scotland's Justice Secretary Michael Matheson said: "It's very important that we take action to improve safety on our roads."
"We know that alcohol is a factor in one-in-ten of road traffic deaths in Scotland, and by reducing the limit we can make sure we get the message to people that drink-driving is unacceptable."
The limit reduction brings Scotland into line with most EU countries.
There are proposals in Northern Ireland to follow suit, but there is no such thirst for change south of the Scottish border.
Asked whether this might cause cross-border confusion for motorists, Mr Matheson replied: "People have a responsibility as drivers to make themselves aware of the regulations and rules of the country in which they're driving."
"We have different laws in Scotland over a range of different matters so it's important that anyone visiting Scotland is made aware of that."
There has been a information campaign to alert drivers to the change, using public information films and roadside signs.
The limit is not being reduced to zero because some people have alcohol in their system because of some medicines and even mouthwash.
The lowering of the limit has been broadly endorsed by road safety campaigners and motorists group, although the Institute of Advanced Motorists has given a qualified welcome.
It would have preferred a sliding scale of punishments, in line with practice on the continent.
Spokesman Neil Greig said: "We've got two main concerns. The first one is that if the police are catching people at this lower limit, then some of the people who actually cause crashes, who are two or three times the limit, they might be getting away with it."
"The second concern is that, in Europe, there are actually sliding penalties. It's like a speeding ticket at the lower limit."
"We don't have that in Scotland, we've got these stringent penalties and we might start to see a fall in support as people start to realise how important these penalties are and how difficult it's going to be, even if you are caught at the lower limit."
