An unidentified vehicle struck the bottom of a railroad overpass in Austin, Texas, and severely damaged one of the concrete beams in the overpass structure. The damaged beam was removed and taken intact to the University of Texas at Austin where the spectral analysis of surface waves (SASW) method was used to delineate nondestructively the damaged zones. SASW measurements performed on the overpass beam revealed a significant velocity contrast between damaged and undamaged zones. Damaged zones exhibited velocities ranging from 4,000 to 6,900 ft/sec (1,200 to 2,100 m/sec), depending on the extent of cracking. Velocities of undamaged zones ranged from 7,100 to 9,000 ft/sec (2,150 to 2,750 m/sec), with most values around 7,800 ft/sec (2,400 m/sec). The measurements were consistent with visual inspection of the beam. More important, the measurements indicated the presence of cracking that was not visually detectable.