(21)Emergency vehicles, namely vehicles used for the purpose of maintaining public safety and order, including by providing immediate assistance during natural or man-made emergencies, such as police vehicles, ambulances, civil protection and rescue vehicles, or fire brigade vehicles, might present particular characteristics, such as being heavier due to special equipment, and might need to benefit from certain derogations from the general rules for a category B driving licence in order to respond efficiently to crisis situations and to rescue needs. Moreover, in order to avoid potential obstacles to the cross-border circulation of such vehicles while they are being used for cross-border interventions in various regions within the Union, Member States should be able to authorise, temporarily or indefinitely, those emergency vehicles being driven on their territories with a category B driving licence. In that regard, Member States are encouraged to mutually recognise national measures, so that cross-border emergency operations are not hindered or penalised.