Enhanced Bridge Replacement Cost Models for Indiana's Bridge Management System

Bridge managers have a duty to monitor and update the costs of bridge preservation activities and to implement cost-effective actions that are in the best interests of taxpayers. This paper presents details of replacement cost modeling for each bridge component (superstructure, substructure, approach, and other costs) for bridges with concrete slab, concrete beam, or steel superstructures. This was done with recent bridge construction data on the Indiana state highway network. It was determined that costs other than substructure and superstructure costs accounted for more than one-half of total replacement cost. The present study supports earlier studies by asserting that basic bridge characteristics such as type, length, and deck area may generally be used to derive reliable estimates of bridge replacement costs. The study also shows that economies of scale can play a significant role in reliable bridge cost estimation. It was determined that the average overall unit cost of replacement for steel superstructure bridges was generally lower than that for concrete superstructure bridges. It was seen that differences in replacement costs across bridge types are attributable not necessarily to cost differences in material and construction procedure only but also to economy-of-scale effects. Cost models can be used to predict total costs of future bridge replacements and are therefore useful for vital bridge management functions such as needs assessments, budgeting, and programming.