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OECD test codes were developed on the basis that the energy to be absorbed by the ROPS during an overturn is proportional to the tractor mass. The selection of the tractor mass used as a reference for the calculation of this energy determines the result of the tests. SAE Standard J2194 and the OECD codes/ISO standards/EU directives generally use the unballasted mass of tractors, but SAE Standard J1194 uses the maximum gross machine mass. We used 300 tractor models to compare the safety provided by the two different methodologies for testing ROPS: OECD Code 4 and SAE J1194. It was possible to establish that SAE J1194 provides a higher level of safety than Code 4 for tractors having ballast greater than 35% of their unballasted mass. SAE J1194 is more demanding with light tractors than with heavy tractors and, as the tractor mass in the moment of overturning can be very different from its unladen mass, it is more in line with the current situation of modern tractors. OECD Code 4 provides the same safety level for light and heavy tractors, but the level of real safety depends on the quotient between the maximum admissible and unballasted masses. Because of that, OECD Code 4 is valid for tractors having moderate ballast, but for highly ballasted tractors its validity is very doubtful.