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A comparative numerical study of motorcoach rollover resistance under ECE R66 and proposed NHTSA regulation conditions

Abstract Under increasing public concern for the safety of passengers in large passenger vehicles such as buses and motorcoaches, legislative regulations are enforced and continuously updated worldwide. Recently, a new federal regulation was proposed in North America to enhance the safety level of motorcoach passengers under the rollover condition, based on regulation No. 66 of the Economic Commission for Europe (ECE R66), but with more severe loading conditions in the form of the full passenger mass ballasted to all seats. This article presents the results of a comparative study on rollover resistance and energy absorption distribution of a motorcoach structure for loadings of both zero and full passenger mass. Two test conditions are numerically simulated using a complete validated finite element model of a typical motorcoach. The results of the comparison indicate that the test conditions of the proposed regulation with full passenger mass lead to a 4.7 times greater penetration of the surviving space of the passenger compartment than the ECE R66 conditions with zero passenger mass. The distribution of the energy absorption suggests that pillar loops rank first in absorbing energy. Owing to the coupled passenger mass, the National Highway Traffic Safety Administration (NHTSA) proposed regulation places higher requirements on the rollover resistance of the wall beams and seat-wall joints, as their energy absorption ratio at the end of impact increases by 27%. Overall, the results of the study can provide a data basis for the manufacturers to improve the rollover resistance of motorcoaches.