| UN R51 Vehicle Noise | Vehicle Noise Emissions | Uniform Provisions Concerning the Approval of Motor Vehicles having at least Four Wheels with regard to their Noise Emissions Vehicle Noise Vehicle Noise Emissions UN Regulation No. 51 UN R51 | UNR | 51 | |
| UN R41 Motorcycle Noise | Motorcycle Noise | Uniform Provisions Concerning the Approval of Motor Cycles with regard to Noise The proposal for the 04 series of amendments, adopted at the June 2011 Forum session, will be posted as Revision 2 to the regulation pursuant to the completion of administrative formalities. Motorcycle Noise Motorcycle Noise UN Regulation No. 41 UN R41 | UNR | 41 |