In this research a statistical relation was sought between the skidding resistance of road surfaces and the relative road risks. In the concept of accident quotient the number of accidents that occurs on a certain section of road within a certain period of time is related to the total number of kilometres travelled on that section in the period concerned. The involvement quotient is the number of vehicles which, per million vehicle-kilometers travelled, subdivided into the categories passenger cars and goods vehicles, has been involved in an accident on a certain road surface. In order to eliminate influences other than skidding resistance, a distinction has been drawn between two types of road. Type I comprises roads with dual carriageways. Type II, which is a more discontinuous type, comprises all the other roads. The accident data (60,000 accidents) were based on records kept by the police. Vehicle-kilometers have been calculated only in so far as they were travelled during rainfall or, alternatively, when non rain was falling. The accidents which occurred on a wet road surface, but not during rainfall, constitute a situation concerning which little can be said with certainty and have been assigned to the skidding resistance class of the wet road and to the class of dry road surfaces too. It appears from the research that each lower skidding resistance class is associated with a higher accident quotient. On the evidence of the statistical relation that has been found the highest possible skidding resistance is to be recommended for both types of road. (A)
Samenvatting