The objective of this paper is to propose the planning methodology for an efficient road preservation investment, giving equal importance to, and integrated consideration of, roadway, bridge, and road slope. Hence, the author proposes to adopt the economical indicator for potential annual loss (ALp) of a road segment. It is desirable to prioritize the road segment for preservation investment based on the total ALp, due to roadway and bridge deteriorations, and road slope disasters.
ALp of roadway deterioration can be estimated using the HDM-4 software developed by World Bank. The authors formulated the estimation tool for ALp due to road slope disasters. The tool was utilized on selected mountainous highways in the Philippines and Nepal. It can estimate potential disaster frequency by summing up frequency scores, consisting of numbers of disasters per year as contributing factor categories of factored items. Moreover, the frequency scores are assigned through multiple regression analysis, minimizing residual sum of squares between actual/potential frequencies of disasters.
A disaster magnitude is assumed to be different depending on the magnitude of the induced cause (heavy rain along a road segment). In order to obtain accurate ALp, plotting a risk curve would be useful. Said curve consists of vertical axis as the exceedance probability per year, and a horizontal axis as the loss. ALp is then estimated using an integral computation from the risk curve, in a year range of asset management.
These techniques ensure more efficient investments in road asset preservation program.