The performance of a vehicle structure in an accident situation can be estimated by determining the correct collapse mechanism and energy absorbing capacity of the deforming components. In most framework-type vehicle structures /buses, special purpose vehicles, passenger compartments in cars etc./ the bending failures of components are clearly dominant, and the energy absorbing material is usually concentrated in the relatively small "hinges" of the collapse mechanism.The paper discusses various modes of the bending collapse that have been observed in practice. The analytical method to estimate the moment-deflection relationship of box beams in bending is reviewed, and the results compared with data obtained by laboratory testing of components.The present results indicate that hinge properties have important effects on the energy absorption. The bending collapse mechanism of box beams is very repeatable in both static and dynamic conditions. The hinge mechanism includes folding and rolling deformation of the walls and the yield line theory was combined with a mathematical model of the mechanism to estimate the moment/hinge rotation relationship.Good agreement between analytical and experimental data has been obtained. The method provides the designer with a reasonable estimate of the behaviour of box beams of known dimensions and material.