As the needs for transportation systems change, the loading requirements and demands on the transportation infrastructure also change. This has resulted in increased number of bridges that are labeled structurally deficient or functionally obsolete since many of the bridges were built prior to present loading requirements [1]. Many of these bridges are open to vehicular and railroad traffic but only at posted loading limits or at reduced speed limits. In order to best use the existing bridge resource and/or schedule repair or replacement strategies, methods need to be developed to assess the actual condition of these transportation structures.