This paper deals with the issue of a trigger design and its performance. In this respect, a numerical investigation is carried out to study the effects of the geometrical features of a bump type trigger on the crush behavior of an energy absorbing member subjected to axial impact loading. The member was constructed by joining a top hat profile with a flat lid. The trigger was considered to be a bump with a semi-circular cross section on the hat profile. The finite element solver, LS-DYNA was used in all crush simulations. As a result, the introduction of the trigger was found to be effective on the peak crush force and the energy absorption capability of the member under axial impact loading. It was also shown that the crush response could be controlled by varying the location and the geometry of the trigger. (C) 2008 Elsevier Ltd. All rights reserved.