The percent of bridges built annually since 1950, with prestressed concrete, reinforced concrete, structural steel, and timber is depicted in Fig. 1. Data plotted are extracted from the National Bridge Inventory (NBI) as of December 1998. These data are compiled annually from bridge inspection results. The data are collected by each state, forwarded to the Federal Highway Administration (FHWA), and maintained as the NBI database.

One measure of bridge's performance is its "structural deficiency" as defined by FHWA. This definition is based on bridge inspection results maintained in the NBI data. The percent of structurally deficient bridges of prestressed concrete, reinforced concrete, structural steel, and timber is plotted in Fig. 2. Again, the data are extracted from the NBI database as of December 1998. The excellent performance of concrete is evident in the plot. Concrete has enjoyed great success in competing in today's "lowest first cost" method of material selection in the US. As steps are taken to consider life-cycle cost for bridges, it is anticipated that the low maintenance required for Concrete will make it an even more desirable material of bridge construction in the US.
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