United Nations Economic Commission for Europe (UN ECE) Regulation No. 138 on Quiet Road Transport Vehicles (QRTV) with regard to their reduced audibility was first published in 2016, and requires pure electric vehicles, fuel cell hybrid electric vehicles and hybrid electric vehicles capable of operating without their internal combustion engine running to be fitted with an Acoustic Vehicle Alerting System (AVAS). These AVAS are sound generating devices which emit sound whenever the vehicle is operating at low speeds to warn pedestrians and other vulnerable road users of the vehicle’s presence. UN ECE Regulation No. 138 specifies detailed requirements and test procedures on the operation and performance of these Acoustic Vehicle Alerting Systems (AVAS).
In the years since UN ECE Regulation No. 138 was first implemented, many vehicle manufacturers, Technical Services and Type Approval Authorities have gained experience with the application and interpretation of the requirements specified within this Regulation and, during that time, some ‘deficiencies’ in the those requirements have been noted.
Recognising that it would be expedient to revise UN ECE Regulation No. 138 to address the ‘deficiencies’ noted during its application, in February 2022, the UN ECE Working Party on Noise and Tyres (GRBP) set up a specific Informal Working Group (IWG) to develop the necessary amendments to UN ECE Regulation No. 138. Between May 2022 and September 2023, this IWG met ten times, and the results of the work undertaken by this IWG were published as an 02 Series of Amendment to UN ECE Regulation No. 138, which came into force on January 10, 2025.
The changes introduced by the 02 Series of Amendments to UN ECE Regulation No. 131 are quite extensive, but the main changes can be summarised as follows:
- More detailed requirements relating to the AVAS test procedures and measurement methods are introduced to ensure consistency of application.
- The vehicle speeds at which the AVAS must generate sound are more clearly defined, both in forward and reverse directions.
- Clarification that the AVAS may generate sound at speeds outside the mandatory speed range is added, along with requirements covering such optional activation.
- Requirements on situations where the AVAS must generate sound when the vehicle is stationary are added.
- A requirement that, when the vehicle manufacturer provides driver selectable alternative AVAS sounds, the vehicle manufacturer must provide a declaration to confirm that all non-tested sound modes comply with the requirements of ECE 138.02 is introduced.
- A new provision is introduced which permits an audible reverse warning system which is type approved to UN ECE Regulation No. 165 on audible reverse warning signals to be used to comply with the ‘reverse direction’ requirements specified in ECE 138.02 for vehicles falling within the scope of UN ECE Regulation No. 165.
- Additional provisions are introduced to ensure that there are no contradictions in the applicable minimum sound level requirements specified in UN ECE 138.02 and the maximum permissible sound level requirements specified in UN ECE 51.03 for vehicle speeds which fall within the scope of both Regulations.
With regard to introduction dates, the transitional provisions contained in ECE 138.02 specify that, compliance will become mandatory for new type approvals from September 1, 2026, and will become mandatory for all new vehicles from September 1, 2028.