The United States highway transportation infrastructure is critical to our nation’s economy. Bridges form a vital part of this important segment of national infrastructure. As bridges vital to the nation age, extended exposure to the elements results in severe corrosion. As deterioration advances, bridges may be taken out of service altogether, resulting in significant economic losses. Current manual bridge inspections may miss some effects of corrosion deterioration, stress corrosion cracking, and other structurally important defects. Structural Health Monitoring (SHM) using deterioration detection is an emerging method for determining the condition of a bridge to help improve the service life and ensure public safety. This project develops degradation indices for steel bridge elements. The Government Bridge has been rendered as a finite element model. An updated model will use data gathered from corrosion tests conducted in a salt fog chamber at the US Army Corps of Engineer’s Construction Engineering Research Lab. The corroded specimens will then be tested in a model truss bridge at the University of Illinois. Using the truss model bridge and the corroded specimens, the effectiveness of damage detection algorithms will be tested in the laboratory and ways to correlate the degradation indices to the AASHTO Guide for Commonly Recognized Structural Elements will be evaluated. Ultimately SHM data from the Government Bridge will be analyzed using these correlated indices. The degradation indices will be incorporated into bridge condition assessment methodologies to provide for more efficient and effective decision making by engineers responsible for bridge operations and safety.