Missing the point on alcohol and accidents

YOUR recent contributors on the drink-driving issue missed the point – if Dr Declan Bedford’s statistical methodology is incorrect, the conclusions are wrong.

According to his statistics, 37% of road casualties have “measurable amounts of blood alcohol” (this could mean as little as a teaspoonful of wine). But this does not prove that 37% of crashes are caused by alcohol.

According to Dr Bedford’s figures, the average Irish adult consumes the equivalent of more than two pints of beer a day. Because it takes a day or more for alcohol to disappear completely from the bloodstream it is reasonable to assume that a sizeable proportion of those on the road at any time have “measurable amounts of blood alcohol”. I have no idea what this figure is, and neither, apparently, does Dr Bedford, but without knowing this we can have no idea of the role of alcohol in crashes. If, say, 37% of people driving, walking or cycling have “measurable amounts of blood alcohol”, we could conclude that alcohol makes no difference. On the other hand, if it is 17.5% then we could say it makes a crash twice as likely, which would mean that only half of these crashes are “alcohol-related” and the other half are due to other causes.