MODELING THE COSTS OF BRIDGE REHABILITATION

Intermediate and long range planning for Departments of Transportation necessitates the estimation of the cost of bridge rehabilitation, a r ange of activities falling between maintenance and replacement. This p aper presents a set of regression models designed within the context o f data available to the New York State Department of Transportation. T he nature of the data necessitated the use of non-linear regression mo dels which were developed using the software package TRIO. Various app roaches were explored in an effort to determine which group of models performed best. For each approach models were developed for estimating separately the cost of rehabilitating the major bridge components: de ck, superstructure, and substructure. One approach involved estimating costs of each component for the entire bridge. Another approach invol ved unit costs. In addition models were developed which allowed compar ison of the predictive power of using low bid vs median bid as the dep endent variable. Furthermore models were developed separately for brid ges with single spans and those with multiple spans. The approach that consisted of working with the costs for the entire bridge consistentl y performed well. In many cases the relationship between the dependent variable (cost) and the predictor variables was highly non-linear. Du e to differences in data availability and definitions the models canno t be applied directly by states other than New York. However, the proc edures followed and approaches employed should provide guidance to tho se wishing to generate models to estimate bridge rehabilitation costs. (C) 1997 Elsevier Science Ltd.