1. ABSTRACTA rollover accident of a bus or a coach is particularly dangerous. Many different aspects must be taken into account in order to reduce occupant injury. The most important criteria are structural resistance, occupant restraint systems and seat anchorages. Spain has complied with ECE R-66 since 1992. For this reason, bus and coach manufacturers have had to improve the structural resistance.IDIADA has developed a simulation procedure using finite element analysis for studying the structural resistance during a rollover. Experimental tests of a representative section of the structure and bending tests of the different beams are conducted in order to evaluate the analysis simulation. Due to the close correlation between the simulation and the real test, IDIADA is currently capable of fully developing structures which comply with ECE R-66 without actually performing a rollover test. The solutions adopted permit the construction of highly resistant, lightweight bodywork, in keeping with current design trends.In this paper, the simulation analysis procedure used by IDIADA is described and the main design criteria for structural resistance are explained.