A research team from UIUC will develop and demonstrate the capability of a nondestructive testing system, comprising measurement hardware, software and an analysis approach, to quantify lateral mechanical track compliance in situ. The measurement approach is based on impulse-driven rail structure vibrations. The hypothesis that underlies the basis of the test approach is that the linear and non-linear fundamental (lowest frequency) lateral vibration response will provide effective measures of lateral track mechanical response that comprises contributions from the track, connections, ties, and subgrade interaction. The proposed research framework aims to address the long-standing challenge of effective track stress management for rail buckling prevention under the assumption that lateral mechanical track capacity plays a significant role in track buckling behavior. The proposed framework incorporates innovative non-linear analysis of nondestructive testing (NDT) vibration method that does not require additional baseline measurements or track modification.