The IWG RD-ASEP Informal Group is developing a mandatory test procedure for UN R51 to assess vehicle noise emission compliance under conditions other than Annex 3, ensuring no defeat device schemes exist. The Editing Task Force created a consolidated R51.04 draft incorporating Supplements up to Supplement 11, with mandatory random RD-ASEP testing for approval and revised control ranges. R51.04 RD-ASEP expands vehicle speed range to 1-100 km/h, adds vehicle performance criteria, implements random test points, and requires testing for approval. Working document submission is expected September 2027, with expected adoption February 2028.

Proposal to amend UN R51 in the 04 series of amendments based on GRBP-84-07, adding definitions and specifications for Real Driving Additional Sound Emission Provisions applying to vehicles of categories M₁ and N₁, modifying sound measurement methods and test procedures including indoor testing provisions, establishing a sound expectation model for RD-ASEP compliance evaluation, introducing provisions for vehicles equipped with an Automated Driving System, and updating Annexes 3 through 10 and associated appendices with revised test conditions, gear selection flowcharts, temperature and test-track corrections, tyre rolling sound measurement procedures, compressed air noise assessment, and conformity of production checks. No Contracting Party shall refuse to grant type-approvals under the 04 series of amendments from its entry into force until [TBD date], after which approvals under the preceding 03 series may no longer be accepted.

Proposals for earlier series of amendments those may be used in certain country
where R156-01 is required. The provisions regarding provision of information on hardware and software relevant to approval testing are moved to the section related to specifications and/or tests as instructed in R.E.3. and the amendment made by WP29-197-06 is reflected.

Proposal for a Guideline regarding the Interpretation of Paragraph 6.2.3. ASEP in the 03 series of amendments to UN Regulation No. 51, updating Informal Document GRB-68-03 and based on GRB/2005/5 and GRB/2010/9. Part A addresses internal combustion and hybrid vehicles when the combustion engine is operating, defining typical on-road driving as vehicle speeds between 15 km/h and 100 km/h, accelerations not exceeding 2 m/s² and vehicle performance not exceeding 35 m/s², and engine speeds of at least 1.5 times idle speed and not exceeding the maximum outlined in Annex 7. Significant deviation means sound level exceeding reference values by at least 6 dB(A). Type approval test results derive from Annex 3 or Annex 7 values, with reference values established using regression curves or calculation principles. Part B addresses electric and hybrid vehicles propelled electrically only, extending guidance to electrified vehicles and Enhanced Exterior Sound introduced by Supplement 11. Typical on-road driving for electric vehicles includes vehicle speeds greater than 0 km/h and up to 100 km/h and standstill covered by UN-R 138. Significant deviation for electric vehicles is at least 3–6 dB(A).

Proposal to amend para. 6.2.1.1. to permit testing of vehicle sound either indoors or outdoors with equivalent results, add new Annex 11 specifying indoor testing provisions, amend Annex 1 to insert para. 8.5. and 8.5.1. requiring documentation of test method selected, amend Annex 3 para. 1. to specify sound level meter requirements for indoor testing per IEC 651 and IEC 61672-3, amend Annex 3 para. 1.1.1. to provide calibration procedures for indoor testing per IEC 942:1988, amend Annex 3 para. 1.3. to exempt wind speed monitoring for indoor facilities, amend Annex 3 para. 2.1. and add para. 2.1.4. to specify outdoor and indoor test site requirements per ISO 362-3:2022 and ISO 26101, add para. 2.1.5. specifying indoor ambient conditions, add para. 2.2.7. addressing test mass for indoor dynamometer testing, amend Annex 3 para. 3. to specify outdoor and indoor test procedures per ISO 362-3:2022 Variant A, amend Annex 3 para. 3.1.1. to clarify outdoor testing microphone placement, add para. 3.1.1.4. defining virtual lines and simulated vehicle speeds for indoor testing, and renumber former paras. 3.1.1.4. and 3.1.1.5. as 3.1.1.5. and 3.1.1.6.

Rationale for Figure Part B.5 of GRBP-84-36-Rev.1