(19)In order to contribute to the reduction of greenhouse gas emissions and the improvement of air quality, by facilitating the use of alternatively fuelled vehicles, Member States should be given the possibility to allow, in their territory, holders of a category B driving licence to drive certain types of alternatively fuelled vehicles of which the maximum authorised mass is greater than 3 500 kg but does not exceed 4 250 kg. That possibility to exceed 3 500 kg should be conditional upon the additional mass allowed being exclusively due to the excess of mass resulting from the alternative propulsion systems and should be subject to limitations and conditions intended to avoid negative effects on road safety.