The impact of unseasonable or extreme weather on traffic activity within Lothian region, Scotland

Abstract

Little has been reported on the variation in traffic activity with either unseasonable or extreme weather conditions. This paper reports on an investigation into such relationships for the former Lothian Region (now split into four administrative districts), in Scotland. Daily traffic activity together with meteorological data was gathered for the period between 1987 and 1991. This data was used to develop a simple model to predict traffic activity based on yearly, monthly and daily variations. A similar model was developed to predict meteorological variables based on monthly variations. The differences in the observed and predicted values were used in the 50% test to determine whether or not unseasonable weather was linked to changes in traffic activity. The changes in the average weekday traffic activity, although significant, were less than 3% for unseasonable sunshine hours, maximum temperature, minimum temperature and rainfall. However at weekends there were reductions of more than 4% in the average traffic activity on both the days with the highest rainfalls and the days with lower than expected minimum temperatures. Similar comparisons were made to determine whether or not there were links between traffic activity and extreme weather conditions. There were similar slight but significant changes in average weekday traffic activity with the extremes of rainfall, sunshine hours, maximum temperature and minimum temperature. However there was an average reduction of 10% in weekday traffic activity when snow was lying. At weekends there was an average reduction of 4% in traffic activity on the days with the highest rainfall and an average reduction of 15% on the days when snow was lying.