An energy absorbing device for reducing acceleration transmitted to a seated occupant in a vehicle as a result of a high energy impact. The device comprises a first energy absorbing mechanism having a first dimension in the impact direction and capable of undergoing predetermined elastic deformation in that direction; and a second energy absorbing mechanism having a second dimension in the impact direction, which is smaller than the first dimension by a distance corresponding to that elastic deformation. The second mechanism is loaded with the impact force after the first mechanism has undergone elastic deformation; the second mechanism comprises a material capable of progressive deformation. The device may comprise a restriction mechanism connecting the two plates, adapted to restrict displacement of the first plate relative to the second plate in any direction different from the impact direction.