A bus rollover is one of the worst vehicle accidents that can occur. Because of the large numbers of passengers, the casualties in a bus rollover are often high and severe. The compliance with rollover safety standards for buses and coaches is mandated by law. This paper presents a comparative analysis of the physical meanings of regulation number 66 of the Economic Commission for Europe (ECE R66) and standard number 220 of the American Federal Motor Vehicle Safety Standards (FMVSS 220). This comparison was carried out using a LS-DYNA finite-element analysis. After performing a comparative analysis following ECE R66 and FMVSS 220 assessments, the investigation further demonstrated the distortion configuration of the vehicle superstructure through the absorbed energy and its distribution over the vehicle and in sections of vehicle superstructure as well as the violation of the passenger compartment under the rollover testing conditions of both ECE R66 and FMVSS 220. Great differences were found between ECE R66 and FMVSS 220 in distortion configuration, reflecting differences in capability and rollover testing conditions. These findings provide a means of evaluating bus superstructure strength and provide guidelines useful in the assessment of regulations applied to the evaluation of bus rollover strength.