The Dangers of Drinking and Driving

It is not the aim of this site to play down the risks of drinking and driving. Alcohol and motor vehicles represent a dangerous and potentially lethal cocktail. Although the figures have been falling steadily in recent years, each year in Britain over 400 people are killed in road accidents where excess alcohol is a factor. Thousands more are seriously injured. Being below the legal alcohol limit is no guarantee that your driving ability will not be impaired. At 50% above the limit, your chances of being involved in a fatal or serious injury accident are five times higher than those of a completely sober driver. Twice the legal limit, and that figure rises to twenty times. (See the table below)

Once you have had a few drinks, the only thing that will reduce your alcohol level is time, and plenty of time at that. Your body can only metabolise one unit of alcohol per hour (the equivalent of a half-pint of ordinary strength beer). After a heavy drinking session, you could still be over the limit the following morning, or even much later in the day. There are cases of people being convicted of drink-driving when they had not had a drink for twenty-four hours. Black coffee or hangover medicines might make you feel better, but they will not bring your alcohol level down any quicker.

And if you are so arrogant and thoughtless that you couldn't care less about endangering the lives of others, bear in mind that 60% of the deaths in drink-related accidents are of the drinking driver himself. Drinking and driving really does wreck lives, and the life it is most likely to wreck is your own.

Stay low - stay safe!

If anyone is in any doubt about the potential consequences of driving when drunk, please read this article or this one.

Statistics on Drink-Driving Risk

The principal source of data on alcohol and accident risk is a study carried out by R F Borkenstein and others in the US State of Indiana in 1964 . This was used as the basis for the original UK breathalyser legislation in 1967. The table below is an interpretation of Borkenstein's findings which shows the risk of a fatal or serious injury accident at various levels of blood-alcohol concentration, as compared to the risk for a completely sober driver. This needs to be seen in the context of the fact that the accident risk for a sober driver doing an average daily mileage on one particular day is less than one-sixth the chance of winning the jackpot on the National Lottery, in other words absolutely infinitesimal.

BAC Range
Accident Risk
0-9 1.00
10-19 0.92
20-29 0.96
30-39 0.80
40-49 1.08
50-59 1.21
60-69 1.41
70-79 1.52
80-89 1.88
90-99 1.95
100-119 4.94
120-139 5.93
140-159 10.44
160 and over 21.38

A feature of these figures that has intrigued statisticians is the reduction in accident risk between 10 mg and 40 mg, sometimes referred to as the "Borkenstein dip". This is certainly valid, not just a statistical quirk, and has been reinforced by other studies. However, it is unlikely really to indicate that consuming a small amount of alcohol will make you a slightly better driver. It is probably a combination of the fact that people driving after one or two small drinks are likely to be driving at times when the roads are quieter than average, and that they may try to compensate for the alcohol by making an effort to drive more carefully than usual. But this underlines the fact that, at these low levels, alcohol does not impair driving ability at all.

R F Borkenstein et al: The Role of the Drinking Driver in Traffic Accidents (Bloomington, Indiana University, Department of Police Administration, 1964)

(May 2000)

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