Since 1 November 2007 the Mercedes-Benz Citaro urban buses with the new diesel technology BlueTec®5 have borne the Blue Angel seal of quality.

The technical requirements for receiving the environmental label from the RAL e.V. and the German Federal Environment Agency involve fulfilling certain criteria such as engine exhaust figures which meet the Euro 5 or EEV (Enhanced Environmentally friendly Vehicles) standard, low interior and exterior noise emissions, no use of ozone-depleting substances, low global warming potential in the refrigerants and paintwork free of heavy metals and with less than 130 grams of solvent per square metre.