Abstract
In ECE Regulation 66 - which describes the requirements and test methods of the strength of bus superstructure in case of rollover the test methods are based on the reproduction of a standard rollover accident. This roll-down process can be analysed on the basis of an energy balance.
The deformation of the rings and pillars is strongly related to the kinetic energy, the larger deformation the bigger kinetic energy. On the basis of the energy balance, the stability of the superstructure may be formulated as follows: the kinetic energy increase, which is the result of a further incremental deformation of the superstructure must be smaller than the deformation work absorbed by the main structural elements during this incremental deformation.