Abstract
The UN-ECE Regulation 66. describes the requirements and test methods for the strength of bus superstructures in the case of a rollover accident. More than 15 years practice proved that the Regulation shall be developed, modified. An international ad-hoc expert group - established in Geneva - is working on this task. The author is the chairman of this expert group The main subjects, fields of the modification and this presentation are the followings:
- The measuring of the standard rollover test and its role in the approval process. The principe of equivalence and the use of substituting approval tests.
- The problem of the pendulum impact test as a substituting approval method. The differences in kinematics, kinetics, dynamics and in the energy balance
- The worst case problem, manufacturer freedom and responsibility. The worst case may be determined by the manufacturer, on the basis of three criteria, structural criterion, survival space criterion and reference energy criterion. - The structural criterion is based on the model of load bearing structure (MOLBS) containing rings and connecting elements between them. The rules of the mass distribution and the definition of the reference energy is given. The definition of the survival space will be independent from the seat arrangement.
- The effect of belted passengers on the required strength of the superstructure. The passenger¡¦s behaviour is examined in the standard rollover test: without seatbelt, having 2 and 3pst seat belt. Mathematical formulation is given for the energy increasing when belted passengers are considered. The possible solution may be: considering a certain ratio ¡§k¡¨ of the passenger mass (0 ¬k ¬ 1) on every seat which is fitted with seat belt
- The problem of the geometrically limited deformation is an essential defect of the existing standard rollover test. The high-decker coaches can pass the rollover approval test with positive result, even having a very week superstructure, because the deformation is geometrically limited.
This paper gives technical, scientific arguments, comments to these questions, providing technical, scientific background to the discussions of the expert group. These arguments are based on test results, mathematical derivations and also on accident statistics and analysis. The presentation of this paper, the international discussion of the above mentioned subjects may contribute to the development of Reg.66