System for absorbing the kinetic energy of the frontal impact of a vehicle against an impact attenuator or a barrier terminal on which it is meant to be mounted, the impact attenuator or barrier terminal being of the kind for use on the sides and central reservations of roads and having a structural element that is capable of being displaced in the longitudinal direction of the impact attenuator or barrier terminal as a consequence of an impact, said system comprising: - an impact element or ram comprising a rigid body and consisting of a core, the forward part of which has the form of a wedge, - and a deformable longitudinal metallic profile having a core, wherein the height of the core of the deformable profile is greater than the height of the wedge-shaped forward part of the core of the ram but less than the height of the rear part of said core, said ram being, in use, attached directly or indirectly to said structural element and said deformable profile being, in use, directly or indirectly secured to the ground, such that during an impact, the ram moves along the deformable profile which remains substantially static, the wedge-shaped forward part of the core of the ram functioning as an attack surface producing plastic deformations propagating along the deformable profile, characterized in that - the ram further consists of a base plate which serves as support for said core and which comprises an upper and a lower wing at an end, wherein said upper and lower wings do not cover the entire length of the ram, thereby leaving two openings in the rear part of said ram, - in that the deformable profile is of an open cross-section in the form of a "U", "C", "sigma" or "omega", said cross-section thus consisting of a core and two wings, - and in that, during an impact, as the ram moves along the deformable profile, said attack surface forces the wings of the deformable profile to open and spread out, with both wings of the profile projecting through said openings at the rear part of the ram. - an impact element or ram comprising a rigid body and consisting of a core, the forward part of which has the form of a wedge, - and a deformable longitudinal metallic profile having a core, wherein the height of the core of the deformable profile is greater than the height of the wedge-shaped forward part of the core of the ram but less than the height of the rear part of said core, said ram being, in use, attached directly or indirectly to said structural element and said deformable profile being, in use, directly or indirectly secured to the ground, such that during an impact, the ram moves along the deformable profile which remains substantially static, the wedge-shaped forward part of the core of the ram functioning as an attack surface producing plastic deformations propagating along the deformable profile, - the ram further consists of a base plate which serves as support for said core and which comprises an upper and a lower wing at an end, wherein said upper and lower wings do not cover the entire length of the ram, thereby leaving two openings in the rear part of said ram, - in that the deformable profile is of an open cross-section in the form of a "U", "C", "sigma" or "omega", said cross-section thus consisting of a core and two wings, - and in that, during an impact, as the ram moves along the deformable profile, said attack surface forces the wings of the deformable profile to open and spread out, with both wings of the profile projecting through said openings at the rear part of the ram.