As legal provisions are increasingly taking into account environmental pollution by internal combustion engines, there is a growing demand for new technologies that allow production of marketable drive systems despite tighter emission controls. Compliance with exhaust gas limits expected to be introduced in the long-run can only partly be achieved by means of conventional internal combustion and exhaust gas aftertreatment technologies. Therefore the challenge to be met is to provide the most beneficial trade-off between fuel consumption and emissions while avoiding negative impacts on driveability.