| Vehicle Sound | Vehicle Sound | WP.29 Discussion Topics | Vehicle Sound Vehicle Sound WP.29 Discussion Topic Vehicle Sound | Topic | |
| UN R51 Vehicle Noise | Vehicle Noise Emissions | UN(ECE) Regulations | 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 R138 Quiet Road Transport Vehicles | Quiet Road Transport Vehicles | UN(ECE) Regulations | Uniform provisions concerning the approval of Quiet Road Transport Vehicles with regard to their reduced audibility (QRTV) This Regulation requires an "audible vehicle alerting system" (AVAS) to reduce the risk of collisions with vulnerable road users unable to aurally detect the presence of electrified vehicles. Quiet Road Transport Vehicles Quiet Road Transport Vehicles UN Regulation No. 138 UN R138 | UNR | 138 |