The object of this study was to gather data on the levels of bitumen oxidation found in dense asphalt surfacings. The information was used to determine if the proposal to raise the 100MPa modulus (at 5°C, 9Hz) limit set in the NZ Transport Agency bitumen specification (NZTA M/1:2007) to 120MPa and 130MPa for 60–70 and 40–50 bitumen grades respectively, was appropriate. Samples of dense asphalt manufactured with 60–70 or 80–100 grade bitumen (excluding polymer modified bitumens) were sampled from field sites of varying ages up to 40 years. The oxidised bitumen was extracted and the modulus measured. The research highlighted serious limitations in the current durability test procedure (originally developed for chip seal binders) when applied to asphalt grade bitumens and review and modification of the procedure is required. However, based on the results obtained, setting the durability test limits in the NZTA M/1 bitumen specification to 120MPa for 60–70 and 130MPa for 40–50 grades, as recently proposed is considered reasonable until further information is available.