As a rule the existing approaches for quantifying the funds needed annually are based on a bottom-up approach. Investigations of condition are performed and, on the basis of these investigations, maintenance programs are calculated for a period of up to a maximum of ten years. In order to quantify the funds needed from a network-wide point of view (top-down approach) it is being postulated that the long term average of funds needed for maintenance of the road infrastructure in order for it to be maintained in the long term should be roughly the same as the annual average deterioration. Important in this context is the complementary view of these two approaches.

The method for determining the deterioration shown in this research report was primarily developed for road networks in local communities. The model is based on a deterioration formula whose dependent variables are the replacement value and the ageing coefficient. All the roads in a community are categorised and replacement values and ageing coefficients are set for each category. The chosen procedure is based on a few specific values of a representative community road network and is simple and transparent in its application. The model is also configured in such a way that, if applicable, specific requirements of the community can also be considered in a transparent and comprehensible way. The principles used by the model could also be adopted for other road networks (e.g. district-wide) provided the corresponding parameters for the model were available.