Abstract: A bituminous binder for asphalt road coverings is prepared by homogenizing a blend of bitumen and polyethylene and/or polypropylene in a heated mixing vessel while stirring the blend and melting and dissolving the polyolefin in the bitumen. The blend is heated to a temperature between 260.degree. C. and 310.degree. C. and subjected to forceful mixing under a high shearing force. The homogenization is continued until the polyolefin has been degraded and the viscosity of the homogenized blend has been reduced below the viscosity reduction attendant upon the mere heating of the blend at this temperature.