For better crashworthiness performance, vehicles must protect its occupants by maintaining structural integrity and converting the large amount of kinetic energy into other forms of energy in a controllable and predictable manner in a crash situation. In doing so, lower crushing force would provide better safety for the vehicle occupants. This paper reviews the axial response of “modified” tubular sections with imperfections and fillers subjected to axial impact loads relevant to the field of structural crashworthiness. The use of imperfections sets the mode and initiation of collapse of a tube at a specific location and reduces the maximum crush force, hence improving the energy-absorbing characteristics of tubular structures. The types of imperfections discussed include prebuckle, parallel and dished indentations, cutouts, stiffeners, fillers, and wrapping.