APPLICATION OF A FUZZY ROUGHNESS INDEX TO THE ROAD ECONOMIC DECISION MODEL FOR LOW AADT ROADS IN DEVELOPING COUNTRIES

摘要

The Road Economic Decision Model (RED) is an assessment tool created by the World Bank for the analysis of investments on roads subject to low levels of traffic in developing countries. Of the variables used in this model, roughness is among those showing the highest incidence in the determination of a project`s Net Present Value (NPV). The difficulty in defining roughness, a rather qualitative attribute in this type of roads in terms of a precise figure may lead to biased NPV estimates. This paper introduces the application of a fuzzy roughness index based on simple fuzzy math, which enables the translation of a qualitative, first-hand appraisal of a road´s roughness into a quantitative expression, a triangular fuzzy number, increasing thus the amount of information in the model. As a result, the estimation of net present value is also interpreted in terms of fuzzy math. Investment alternatives for a road may be then compared on the basis of the "representation" of each "fuzzy" NPV obtained for the investment alternatives. An analysis conducted on the basis of fuzzy roughness and fuzzy net present values can lead to select an alternative that is discarded with a standard approach.