A concept of an under-ride guard comprising an energy dissipater is proposed to enhance the crashworthiness of the light-weight vehicles involved in collisions with heavy freight vehicles. The proposed energy absorbing under-ride guard is analytically modeled incorporating non-linearities due to asymmetric damping, stiffness and kinematics of linkages, using the principles of conservation of momentum and Lagrangian dynamics. A performance criteria based upon the magnitude of intrusion of the car mass, car mass acceleration, and dissipated energy is formulated to investigate the performance benefits of the proposed guard. A multi-variable design optimization is performed to minimize a weighted function of performance variables and to determine the optimal asymmetric damping and stiffness properties of the guard. The performance characteristics of the proposed guard are evaluated under direct impact at different speeds, and compared with those derived for a conventional rigid under-ride guard using DYNA3D. The results are discussed to highlight the performance potentials of the proposed guard.