Abstract: Crash attenuator assemblies are operable to decelerate errant vehicles traveling along roadways. The crash attenuator assemblies include guide rails anchorable to a ground surface adjacent a roadway. Frame assemblies are supported on the guide rails and are displaced upon impact by errant vehicles. The frame assemblies are spaced longitudinally along the guide rail such that a bay is defined between adjacent ones of the frame assemblies. A compressible energy absorber is disposed within one of the bays. A piercing device is operative to penetrate into said compressible energy absorber upon compression of the compressible energy absorber during an impact event to create an aperture that is a visually observable identifier of compression of the compressible energy absorber beyond a predetermined compression threshold.