Several approaches are presented in this paper for projecting the budget needed for urban infrastructure renewal, particularly for urban roads, water supply and sewage networks. The approaches used are based on the age and the material the structure is constructed in, its rate of deterioration, any relevant standards and any future requirements. For various reasons trend extrapolations and catalogues of ecological desiderata are inadequate methods for projecting renewal requirements. With the so- called perpetual inventory method, time series of investments are used in combination with survival and depreciation functions of specific elements. However, this method does not take into account choices open to the decision maker relating to the intensity of scheduling of renewal activities. In this respect the pavement management approach has some advantages. Therefore, an interactive impact model is presented which has been developed at Karlsruhe University for infrastructure renewal planning at a network level. Long-term investment forecasts are supplemented by corresponding forecasts of network performance indicators, such as failure costs and real capital values. Thus, network renewal strategies can be developed interactively which consider these effects, prevent renewal peakloads and meet those standards set by the decision makers. Finally, the deterioration of the urban infrastructure is discussed in the broader context of urban development, with particular reference to developing countries, and the extent to which information, methods and funds are available for tackling these problems.
Abstract