This paper describes a new process for co-retorting scrap tyres and waste oils to produce a particular carbonous residue suitable for use as a bitumen modifier. Bitumens modified with such residues were observed to have parallel, similar reinforcement properties to those reported for carbon black-modified bitumens, with additional benefits. The carbonous residue retarded oxidative aging and long-term embrittlement of bitumens. A "natural" anti-stripping agent was incorporated in the residue during the retorting process. Details of the bitumens and bituminous mixtures testing are presented. Examples related to bitumen properties are also discussed. Test results indicated that these carbonous residues enhanced the performance properties of bitumens and bituminous mixtures.