THE word "ice" conjures up wide range of different images. It may bring to mind, for example, ice-cubes in a fizzy drink in summer time, or the Pavlovian tinkle of the rocks in something stronger. One might visualise Torville and Dean on an Olympic ice-rink, or Mr Pickwick pirouetting on the frozen pool at Dingley Dell.
Some of us, on the other hand, think first of various Ice Ages labelled "Little", "Last" or "Great", and go on to contemplate the mysteries of climatic change; and others think big and remember the Titanic, or small and recall a friend who slipped upon some frozen puddle. But particularly at this time of year we are likely to remember ice as probably the most dangerous of the winter hazards awaiting drivers on the roads.
Ice, of course, is only one such hazard. More, like rain, fog, snow and gusty cross-winds, are equally obvious. But careful study suggests that there are still other, much more subtle, weather influences that may well affect our driving.
The human body seems to be well adapted to the regular variations of temperature and humidity that occur naturally in the course of the day. There is evidence, however, that short-term and irregular changes in these elements, of the kind that take place when the weather is dominated by a rapid succession of fronts and depressions, are more difficult to cope with, and may impair certain skills, including driving.
In this context, attempts have been made to classify weather conditions into "biologically favourable" and "biologically unfavourable"
categories, by observing their effect on physical and mental dexterity: it has been found that, in general, our efficiency appears to be greatest in the quiet calm conditions associated with anticyclones, provided it is neither too hot nor too humid, and that low-pressure situations are less favourable from this point of view.
The evidence suggests that weather-related physiological influences like these may affect the frequency of road traffic accidents. The length of time taken for drivers to react to traffic signals, for example, has been measured in various weather conditions, and related to the extent to which the weather is "biologically favourable" or otherwise.
Reaction time was found to be about 10 per cent shorter in favourable weather conditions - enough to have a measurable effect on accident frequency. This tendency has been confirmed by studies carried out in Munich, which showed a 15 to 20 per cent increase in traffic accidents in "biologically unfavourable"
weather conditions, quite overshadowing the impact of ice, snow, fog or any of the other more obvious weather-related factors.