Madam, - Ever since the introduction of the penalty points system in November, 2002, there has been a steady stream of commentaries pointing to the latest apparent increase in road deaths and ascribing it to a failure of that system. The most recent was your own Editorial of May 25th, "Death on the Roads", which began: "The downward trend in the number of fatal accidents over recent years has been reversed". Deeper analysis of the available data tells a different story.
Monthly data on road deaths for the last five years are available on the Garda website. A casual review of these data suggests haphazard variation from month to month, with considerable swings both up and down. More careful analysis reveals a steady decline over the five years with a clear seasonal pattern of more deaths in summer and fewer in winter.
From one month to the next, the numbers of road deaths is as likely to increase as decrease, and by unpredictable amounts, having allowed for the underlying pattern. It seems that commentators focus on the latest apparent increases - for example, January and February of this year when the numbers appeared above average and above the levels of the previous few months. However, the levels were down again in March and April.
Note also that nobody bothered to comment on the October 2003 number of road deaths, the lowest monthly number on record, or on the September 2003 number, the third lowest - both in sharp contrast to September and October numbers of previous years which all registered on the high end of the scale.
In view of this, commentators should avoid commenting on the latest apparently alarming increases in road fatalities and, instead, view them in the context of an evolving pattern.
It would be more useful to analyse the many factors involved in road fatalities over an extended period. - Yours, etc.,
Dr MICHAEL STUART, Department of Statistics, Trinity College, Dublin 2.