Abstract: An improved rib assembly for a crash test dummy includes a U-shaped outer member which simulates a pair of ribs secured to a spine and a pair of transverse assemblies disposed in parallel and coupled between such opposed ribs. A first assembly is a spring centered damper which provides simulated resistance to displacement of one rib relative to another. A second assembly includes a spring biased piston and cylinder that provides simulated positioning of the rib ends. A sensor disposed generally between the two assemblies measures the displacement of one of the pair of ribs relative to the other. The piston rod is supported upon a pair of linear ball bearing assemblies which maintains alignment between these two assemblies and ensures accurate responsive motion therebetween without binding and thus accurate measurements of displacement. A plurality of U-shaped rib assemblies, typically three, may be utilized to simulate a rib cage in a crash test dummy.