Scientific paper ID 2090 : 2021/3

Low visibility is one of the factors for increasing the number of traffic accidents. In the present research we have studied the effect of meteorological events such as fog and mist on the number of road accidents in Sofia, Bulgaria. We compared the number of traffic accidents during days with fog (with visibility below 1 km), mist (visibility from 1 to 10 km) and their number in days with absence of such events. The study period covered more than 1000 dates between October 2001 and February 2009. The results showed that the highest number of accidents occurred on days with mist, followed by foggy days and, expectedly, the lowest average number of accidents was observed in days without such phenomena. The differences in the average number of accidents are statistically significant. The interpretation of this result is related to a change in drivers’ behavior during fog – fewer inexperienced drivers decide to go on the road in such conditions, drivers usually reduce speed and increase the distance between cars in foggy weather. Despite the measures taken, as expected, due to reduced visibility, the number of accidents on foggy days is higher than on other days. Unlike fog, mist is probably an underestimated meteorological phenomenon by drivers and pedestrians.