|Authors:||Peter Christensen, Arild Ragnøy|
|ISBN (digital version):||82-480-0649-2|
The annual expenditure of The Norwegian Public Roads administration on maintenance and resurfacing of roads is considerable. It is therefore essential with knowledge of the effect of the condition of the road surface on the risk of accidents. This is a report of a study of this effect. The condition of the road surface is described by rut depth and roughness (IRI). Changes in cross-slope have also been studied. Two methodological approaches have been tried to establish the relationship between other variables and the accident risk, the most important being logistic regression. An increase in rut dept entails an increased risk. The relationship is not linear. Compared with rut depths lower than 4mm, the risk in all rut depths in all other intervals is higher. Risk is highest in the interval 4-9 mm and above 25 mm where the risk is approximately 20 per cent higher than for rut depth lower than 4 mm. Increased IRI entails an approximately linear reduction in accident risk. The relative risk increases by approximately 3 per cent when IRI increases by 1 mm/m.