The review of the current limit is the response by UK Transport Secretary, Lord Adonis, to a growing campaign by road safety groups to reduce the limit to 50mg.

Changing the legal limit to 50mg would reinforce the message of the unacceptability of drinking and driving and, because it is equivalent to one pint of lager for the average man, it would be clearer that one drink is the limit. However, the possibility of attaching a different

penalty to the new limit risks diluting its effectiveness. At present, anyone caught driving over the 80mg limit faces an automatic

12-month ban, but the review is expected to consider whether someone with between 50mg and 80mg in their bloodstream should face a penalty short of an automatic ban. The mixed message that would send could result in the unintended consequence of the 50mg limit not being taken seriously. An automatic ban is

a considerable deterrent and with polls consistently showing

a majority of motorists in favour of a 50mg limit, it would be likely to meet general acceptance, particularly if it produced the projected outcome of saving around 65 lives a year.

Although road deaths have decreased significantly over recent years – in Scotland, they fell by a half between 1997 and 2007 – the number of drivers over the alcohol limit remains disappointing. During last year’s campaign against drink- and drug-driving over Christmas and New Year, 654 drivers in Scotland were caught driving under the influence of alcohol or drugs. That was a decrease from the previous year, but a large number given the high-profile warnings of increased police activity over the festive season. That suggests that, despite the increasing social unacceptability of drinking and driving, there is a hard core of drivers who believe it is unlikely they will be caught. A 50mg limit is unlikely to change their minds unless it is backed by an automatic ban.

Legislating for drug-driving is a more difficult matter. There is widespread support for roadside testing of drivers suspected of being under the influence of drugs, but making it an offence to drive with a particular level of specific drugs would open a can of legal worms. It would be perceived as effectively sanctioning the use of small amounts of illegal drugs such as cannabis and cocaine, and call into question the whole policy of making some drugs illegal. Nevertheless drug-driving impairs judgment and is a factor in many serious accidents, and our approach of having to prove impairment is out of date. The law needs to catch up with the reality of driver behaviour and a wholesale examination of how to reduce the danger is long overdue.

Improving driver responsib­ility is an educational process, but that can be reinforced by effective sanctions.