Statistically, rollover of passenger bus is generally considered the most severe type of accident in terms of its resulting fatality rate. In a bid to improve the safety standard of passenger bus in Thailand, the Department of Land Transport, the Ministry of Transport, have introduced a rollover strength as part of a requirement on bus approval procedure which will be implemented from 2023 onwards. However, main stumbling blocks are a lack of engineering experience by bus manufacturers to achieve such structural design as well as a limited number of “pass” case in the past. This work was thus initiated by the department of land transport in order to study on a design prospect of bus structure with height exceeding 3.60 m under rollover test conditions according to a European standard, UN R66.

The objective was to obtain an engineering design/ drawing of a bus structure which satisfied a safety standard of UN R66. A Computational-Aided Engineering (CAE) technique was employed as a main tool in this study to simulate a rollover phenomenon for bus structures of interest. A three-dimensional CAD bus model, chosen from selected bus manufacturers, was created before a conversion into a finite element model mainly consisted of shell elements. The main simulation outputs were resulting deformations of structural members for a calculation of a distance between deformed members and a residual space as described in UN R66. Another important part of this prototype was a validation of simulation process used in this work. The validation was done by a comparison to an actual rollover test of a full structure at a testing facility of Department of Land Transport. Once validated, such simulation process was further carried out for a detailed redesign of a sample bus structure until the one which satisfied UN R66 could be obtained.