ACEA proposal for defining a hybrid key function (torque split for parallel hybrids and energy management for serial hybrids) in the configuration of HILS software in the testing heavy-duty hybrid vehicles. ACEA also proposes to exclude “micro” hybrid systems (i.e., 48-v based systems) used to supplement the internal combustion engine as a means to reduce CO₂ emissions and improve fuel efficiency. The exclusion criteria would be based upon the ratio of positive electrical power to total system power (to be defined).