This paper presents a study of the behaviour of eight road binders (one reference bitumen and 7 modified bitumens) used in porous asphalt wearing courses of an experimental road built in 1985. The complex moduli as well as different other characteristics of the binders were determined on the original binders and mixtures. A relationship between the complex modulus of binders and that of the corresponding mixtures has been validated for the case of modified bitumens. The complex moduli as well as different other characteristics of the binders were determined after different exposure times in a laboratory simulated long term ageing test. For some of the binders, these results were compared with the results obtained on tbe binders extracted from cores on the mixes, in service for 12 years. It was investigated whether the complex moduli of the aged mixes could be estimated on the basis of that of the aged binder, with the help of the relationship between the complex modulus of the binders and mixtures.