InfraRed spectrometry is a powerful technique to characterise bituminous binders. The methodology is not fully harmonised and may lead to vari-ability. The RILEM-272-PIM-TG1, evaluated seven complex bituminous, for which eleven laboratories performed FTIR. While, the spectra showed sim-ilar trends, further analysis was needed to improve comparison. A specific approach was applied on two binders, unmodified and polymer modified bitumen, and two ageing conditioning. Combining a Gaussian distribution
and derivative analysis confirmed a good alignments of laboratory results. A two-step model was developed improving further interpretation. It con-sists of a baseline adjustment with eight points and normalisation over the maximum aliphatic peak. Furthermore, a specific fingerprint model was determined with the main absorption peaks defined by their location and shape. Only the intensity varies from laboratory to laboratory and binders. This general approach can be used as a platform to characterise aging or binder complexity