The goals of this paper are to present mathematical models for evaluating frontal crash compatibility, to investigate and to optimize crash compatibility. Since a slight softer and longer crumple zone is required for heavier vehicles to improve the compatibility, a smart vehicle structure is proposed to support the function of the existing vehicle. The proposed structure consists of two independently controlled hydraulic cylinders integrated with the front-end longitudinal members. The mathematical models of both standard-standard vehicles and smart-standard vehicles in head-on collision are developed and numerically solved. Numerical simulations prove that the smart vehicle brings significantly improvement in vehicle compatibility.