EVENNESS AND SERVICEABILITY OF ROADS

Evenness and serviceability are terms about which, in colloquial language, everybody, can make himself an idea, but which can hardly be defined scientifically. Highway engineers always knew that there is a relation between evenness and the degree of serviceability. At the beginning of the thirties a geometricly-abstractly formulated evenness criterion was introduced in Germany for acception purposes, which is still valid today. In default of profound knowledges, people tacitly thought that this criterion guarantees a maximum serviceability. Investigations by CAREY and IRICK brought a serviceability standard and showed that there can only be a relation between evenness and serviceability if evenness is appropriately defined. While evenness can be defined in an entirely mathematical-geometric way and thus stays independent of epochal influences, serviceability is submitted to temporal ideas. Extensive investigations in Germany confirm the American results. Other investigation pointed out the existence of serviceability index limits which for traffic reasons should be strictly kept at the moment of pavement construction (acceptance) as well as at the end of life of a road.