The IWG RD-ASEP is developing a mandatory test procedure to assess compliance with paragraph 6.2.3 of UN R51.04, ensuring vehicle noise emissions at various speed, load, and acceleration conditions are linked to vehicle physics without defeat devices. R51.04 RD-ASEP expands testing from full acceleration only to any acceleration position, increases vehicle speed range from 20–80 km/h to 1–100 km/h, adds vehicle performance criteria, requires random test points for approval rather than manufacturer declaration, and can test gears and loads previously unavailable. An updated GRB-68-03 will accompany R51.04. Submission targets include informal draft September 2026 and expected working document adoption February 2028, with TOR extension requested through 2028.

An improvement intended to increase vehicle robustness in Annex 3 creates more difficulties in RD-ASEP assessment. Small variations in Annex 3 parameters may result in unexpected substantial exceedances in Annex 7. Minimal changes in the calculated tyre share at the anchor point may cause vehicles to fail Annex 7. The regulation should ensure realistic test effort and workload for compliance verification, as current requirements may require up to 180 combinations per type across test tracks, temperatures, driving modes, and tyres.

RD-ASEP includes technical background and vehicle application guidance for Real Driving Additional Sound Emission Provisions under UN R51.03 Supplement 7 Annex 9 for the mandatory monitoring phase between 07/2023 and 06/2024. RD-ASEP, referenced in GRB-68-03, applies to vehicles of category M₁ and N₁ equipped with internal combustion engines and covers engine speeds up to 95% of typical driving in speed ranges applicable to sub-urban conditions. A Sound Expectation Model predicts vehicle sound levels at randomly selected operation conditions by splitting measured pass-by test results into tyre rolling sound, mechanical no-load sound, and dynamic sound components, using reference values from Annex 3 type approval tests with logarithmic functions and parameter table slopes. Compliance assessment allows measured sound to exceed calculated expected sound by not more than 2 dB for maximum two test runs out of fifteen. Model validation with 2024 monitoring database confirms the tyre rolling sound and power train sound models represent well approved tyres and engines, with less than 5 dB typically separating pass-by run results from the limit.

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.

The agenda includes welcome and opening remarks, introduction of participants and organizations, adoption of the draft agenda, review of minutes from the 13th session of June 2026, review of Terms of Reference from GRBP 78th Session (GRBP-78-13), UN R51 matters, review of report to GRBP, and determination of the date and place of the next meeting, scheduled for 20–22 October in Barcelona, Spain.

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 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.

Proposal to amend Annex 3 and Annex 7 regarding ASEP calculations and temperature corrections:

• Add reference to nMAX and kp factor for ASEP anchor point calculation in Annex 3, Appendix 1 Table 1,
• Clarify temperature correction equations and coefficients K1 and K2 by defining them uniquely in para. 3.2.3. and adding missing index j references in Annex 3, Appendix 2 paras. 3.2.3., 3.2.4., 3.3.3. and 3.3.4.,
• Delete from Annex 7 para. 5.2. a sentence regarding gear ratios for ASEP Lref that was wrongly introduced in Supplement 10 (GRBP-79-33/Rev.1).

Session report of WP.29 (World Forum for Harmonization of Vehicle Regulations), its Administrative Committee of the 1958 Agreement (AC.1), Executive Committee of the 1998 Agreement (AC.3), and Administrative Committee of the 1997 Agreement (AC.4) held 23-26 June 2026 in Geneva. AC.1 voted on 92 amendments to existing UN Regulations, one corrigendum to UN Regulation No. 79, and three new UN Regulations (Nos. 184-186) on liquid hydrogen vehicle safety, automated driving systems, and tyre abrasion performance. AC.3 established UN GTR on automated driving systems and adopted corrigendum to UN GTR No. 9 and Amendment 2 to UN GTR No. 13. WP.29 extended mandates of several informal working groups and noted accession of Mongolia and Armenia to the 1958 and 1997 Agreements respectively.

Task Force Data Analysis held an online meeting on 7 July 2026. The group discussed database analysis, including insufficient data for higher performance and acceleration, and agreed that more data are needed. When new data are generated, operation conditions should focus on higher performances covering the ASEP range, higher accelerations up to and exceeding 5 m/s, pass-by runs with gear shifting, and low speed measurements in the UN R117 AVAS control range. The group reviewed proposals to the TF-Editing based on draft UN R51.04 and agreed some changes, with review results to be uploaded as Rev.1. A question regarding the phrase “but no more than 2.0 m/s” in paragraph 3.1.2.1.4.3 regarding vehicles with only one gear ratio was noted as issue #23 pending further review.

Proposal to add para. 4.4.1. through 4.4.8. to restructure target operation conditions provisions, add para. 4.4.7. to permit acceptance of runs outside the control range under specified provisions, modify para. 3.6.1. to change reference acceleration determination from maximum to selected acceleration for a selected reference v-t-e ratio, modify para. 4.5.4.1. to set negative calculated acceleration values to zero, add heading “Carry-over parameters from Annex 3” to para. 2.2.1.2., add para. 2.2.1.2.1. and 2.2.1.2.2., and modify constant speed test parameters to report vehicle speed vBB’_CRS_ANCHOR rather than reference speed vTEST of 50 km/h.

This presentation, intended for discussion within TF Data Analysis RD-ASEP and not for conclusions, analyzes model performance using L_exp data from Annex_9_test_runs where both left and right sound were measured. Model performance varies across speed bins, with higher mean absolute error at low and high speeds. Adjusting theta_tr values improves mean absolute error across all speed bins. Testing without an envelope function results in more measurements exceeding expected values, requiring extra margins.

The agenda includes welcoming participants, reviewing and adopting the agenda, scheduling next meetings on 7th July and 24th August 2026, analyzing database distance in dB from the borderline, discussing proposals to TF-Editing based on draft UN R51.04 from the June Gothenburg session, preparing wording proposals for items 13–19 from the issues list, and reviewing decisions and work for the next meeting before reporting to IWG RD-ASEP.

This document presents a clean draft proposal for the 04 series of amendments to UN R51 (Noise of M₁–M₃ and N₁–N₃ Categories of Vehicles). The proposal establishes uniform provisions for sound emission approval of motor vehicles with at least four wheels, introducing comprehensive specifications for measuring vehicle noise during motion and stationary conditions. Key provisions include detailed test methods with outdoor and indoor testing options, sound level limits varying by vehicle category and power characteristics, requirements for vehicles of categories M₁ and N₁ to comply with Real Driving Additional Sound Emission Provisions (RD-ASEP), specifications for exhaust silencing systems containing fibrous materials, conformity of production procedures, and specific adaptations for vehicles equipped with Automated Driving Systems. The regulation applies from its official entry into force, with a transitional period allowing acceptance of prior-series approvals until a specified date.

IWG RD-ASEP is developing a mandatory test to assess compliance with paragraph 6.2.3 of Regulation 51.04 main body, assuring vehicle noise emission at speed, load, or acceleration conditions other than Annex 3 condition is linked to vehicle physics with no noise emission test detection or defeat device schemes. After the 13th session in June 2026, the Editing Task Force created a consolidated R51.04 draft incorporating R51.03 Supplements up to Supplement 11, with mandatory random RD-ASEP testing for approval and revised control range. Submission targets include informal document first draft September 2026, second draft February 2027, and expected working document for adoption February 2028.

The Task Force Data Analysis held 14 meetings, with 12 used to eliminate database errors and 2 to begin data analysis. The analysis revealed the need to better understand the concept and history of RD-ASEP development. Questions were raised regarding whether RD-ASEP should follow envelope functions framing typical sound behaviour of vehicle components or average behaviour with acceptable tolerance. Comparing databases from 2017/2020 and 2023/2024 showed different pass/fail rates across vehicle types. The group seeks clarification on RD-ASEP model optimization, accuracy expectations, and documentation explaining historical background and parameter selection.

Proposal to insert paragraphs establishing references to Software Identification Number definitions in Consolidated Resolution R.E.3 Annex 7 para. 2, insert paragraphs requiring manufacturers to provide Technical Services with information on hardware and software influencing performance, insert paragraphs allowing vehicle manufacturers to apply for new approvals to differentiate software versions for registered vehicles from those for new vehicles with duplication of tests avoided where possible, amend production discontinuation provisions to clarify that production is not considered definitively discontinued if manufacturers intend to obtain subsequent extensions for software updates of registered vehicles, and amend approval communications to include additional information regarding software identification and software updates in UN Regulations 51, 64, 138, 141, 142 and 165, as presented in document GRBP-83-36 and implementing Revision 8 to Consolidated Resolution No. 3 (WP.29/2025/147).

This document provides guidance for interpreting paragraph 6.2.3 of UN R51.03 concerning Additional Sound Emission Provisions for vehicles of category M₁ and N₁. Part A clarifies that typical on-road driving means driving at speeds between 15–100 km/h with accelerations not exceeding 2 m/s² and vehicle performance not exceeding 35 m/s, across any gear except reverse at engine speeds of at least 1.5 times idle speed and not exceeding the maximum specified in Annex 7. Significant deviation is defined as a sound level exceeding the reference value by at least 6 dB(A). Type approval test results derive from Annex 3 or Annex 7, with reference values determined using regression curves for Slope-Assessment or calculation principles for Lurban-Assessment. Part B addresses electric and hybrid vehicles when electrically propelled, extending ASEP scope under Supplement 11, applying comparable principles with modifications regarding active sound enhancement systems and operating speed ranges between 20–100 km/h for electric vehicles.

The agenda includes discussion of Terms of Reference from GRBP-78-13, procedural update from GRB-68-03, Analysis Task Force Report, Editing Task Force Report, R51.04 Issues List Review, draft R51.04 text review, Inside and Outside Boundary Condition discussions, and confirmation of next meeting date and place as August 31–September 1 in Geneva, Switzerland.

Current RD-ASEP derives the regulatory level based on the certified value without accounting for margin against regulatory values of the certified value. RD-ASEP additionally regulates partial acceleration, unlike current ASEP which only stipulates full-throttle acceleration. It is proposed that RD-ASEP should take into account a margin against the regulatory values of the certification values, similar to current ASEP, to prevent quiet vehicles such as BEVs from being unfairly deemed NG.

In vehicles with automatic transmissions, upshifts during testing cause SEM expected values to be exceeded. The proposal addresses three cases: vehicles with non-locked gear ratios, vehicles with locked gear ratios, and vehicles with only one gear ratio. For Case 1, such data does not meet conditions in R51-03 Annex 9 “4.5.2. Non-locked transmissions” and require no SEM correction. For Case 2, the proposal adds text to Annex 9 (7), Appendix 1, paragraphs 3.4. and 3.5., permitting substitution of maximum engine speed nMAX(AA-BB)TEST for nBBTEST when the maximum engine speed between AA’ and BB’ exceeds the engine speed at BB’.

The agenda includes a review of the schedule with next meetings on 7th July and 24th August, continuation of database analysis presentation from RDW, review of decisions and work for the next meeting, report to IWG RD-ASEP.

Task Force Data Analysis (Sub Group to IWG RD-ASEP) held its 13th meeting on Wednesday, 3rd June 2026. The group reviewed database analysis including statistical analysis of differences between expected and measured sound levels, sub-model construction, and optimization calculations for parameter tables. Discussion addressed model construction concerns, vehicle failure differentiation, and data collection requirements including approval values according to UN R117. Next meetings are scheduled for Tuesday, 7th July and Monday, 24th August 2026.

This presentation analyzes RD-ASEP model performance using test run data from Annex_9_test_runs where both left and right sound were measured. Current model shows 1.3% of measurements above L_exp; without the 2 dB margin this increases to 8.4%. Model overestimates at low speeds and underestimates at higher accelerations. Tyre rolling sound parameters have most influence on results and dominate most of the data set. Optimizing all 13 parameters reduces mean absolute error from 2.1 to 1.1 dB. More high acceleration measurements are needed to reliably calibrate the dynamic component.

The IWG RD-ASEP informal group is developing a mandatory procedure for UN R51 after the monitoring phase. The Analysis Task Force determined vehicle databases and expectation model are suitable for RD-ASEP use. The Editing Task Force created a consolidated R51.04 draft incorporating R51.03 Supplements up to Supplement 11, with revised manipulation and defeat device provisions and mandatory random testing for approval. R51.04 RD-ASEP expands vehicle speed range to 0-100 km/hr, adds vehicle performance criteria, requires testing for approval, and permits random test points and any acceleration position, compared to R51.03 ASEP.

Corrections to documents submitted by TF-AVRS and approved by GRBP amend terminology in UN R51.03 to harmonize bidirectional spelling, correct vehicle category references in UN R51.03 and UN R165 to reference category X only rather than non-existent category M1Y or category M, clarify in UN R64 that logical signals shall be transmitted to the ADS when an ADS feature is active, introduce references to specific ADS provisions in Annexes 5 and 7 of UN R138.02 and UN R165, add grammatical corrections to UN R141, and align UN R165 terminology with ADS regulation language.

The session will cover database analysis including review of documents and discussion points from pilots view, AVAS term dL Dynamic factor x, review of decisions and work for the next meeting.

The 20th session of the Task Force on Vehicle Sound convened on 14 April 2026. The session adopted the draft agenda and reviewed the 19th session report with a minor correction. The cross-matrix, defined in 2021 to assess traffic noise reduction policies through traffic scenarios and models, was rediscussed. A model based on RD-ASEP monitoring data was presented, showing significant deviations from EU-CNOSSOS predictions. Additional data are needed for M₃/N₃ and L-category vehicles. Extension of the cross-matrix to L-categories was proposed, utilising data from UN R41-06 RD-ASEP. A subgroup was established to develop scenarios, particularly for L-categories, and review available models. The next meeting is scheduled for 9 June 2026.

Japan comments on the draft 04 series of amendments to UN R51 (Noise of M₁–M₃ and N₁–N₃ Categories of Vehicles). Japan highlights several editorial and technical issues. Regarding para. 2.24.1, Japan suggests the table of symbols for Annex 3 should state symbols are “used for the first time” consistent with ISO standards. For para. 3.1.2.1.4.3, Japan requests deletion of “but no more than 2.0 m/s²” as unnecessary for RD-ASEP applied to electric vehicles. Japan notes para. 6.2.3.4 should reference appropriate appendices for the RD-ASEP statement of compliance requirement. Paragraphs 11.1.4 and 11.1.5 are identical and one should be deleted. Japan flags para. 3.2.3.4.2 requires tyre conditioning on outdoor test tracks for indoor testing. For Annex 6, para. 3 should clarify that compliance assessment references para. 5 of Annex 7 for expected sound pressure level limits applicable to conformity of production testing.

The IWG RD-ASEP informal group is developing a mandatory procedure for UN R51 after the monitoring phase. The Analysis Task Force determined vehicle databases and expectation models are suitable for RD-ASEP development. The Editing Task Force created a consolidated R51.04 draft submitted to GRBP-84. The revised R51.04 RD-ASEP includes manipulation and defeat device provisions, mandatory random testing for approval, revised control range, any acceleration position testing, vehicle speed range 0-100 km/hr, and vehicle performance criteria. A revised companion document GRB-68-03 is necessary.

The Task Force Data Analysis held its 12th session on 28 April 2026. Database version 3 requires further corrections to reflect IWG decisions on v_test, parallel and serial hybrids, and German input; version 4 will be delivered. The group reviewed German input on database issues and decided to establish an Excel list documenting observations, background information, and proposed solutions. Additional data are needed on gear shifting during pass-by measurement, ICE ON/OFF shifting, low speed measurements below 30 km/h, high performance vehicles with acceleration greater than 5 m/s² at high speeds, and EV data.

Results of the review of proposals for UN Regulations R28, R51, R64, R138, R141, R142, and R165 regarding autonomous vehicle readiness. Key findings include: inconsistent Mass in Running Order definitions between R51 and R138 versus RE3; unclear special testing provisions in R64, R138, and R165; need for clarification on ADS optical and logical signal transition in R64; redundant full definitions from RE3 in multiple proposals should reference RE3 via footnote instead; inconsistent ADS activity terminology across R64, R141, and R165 should be standardized; incorrect Category Y references in R51 Table 2; and definition and spelling errors in R51, R138, R141, and R165.

The RD-ASEP Informal Working Group met April 14-16, 2026 in Berlin. The Analysis Task Force concluded data cleaning and will use data to answer questions and update the parameter table. The original aim of RD-ASEP was to address vehicles with louder partial throttle than full throttle results. The Editing Task Force reviewed draft R51.04 and was directed to provide an updated draft for the June meeting, replacing the old Annex 7 with the current Annex 9. The Chair requested the Editing Task Force prepare a summary report to GRBP for September evaluating the monitoring database, Expectation Model, and draft R51.04.

The 21st session of the Task Force on Vehicles Sound will be held on Tuesday 9th June 2026 from 13:00 to 17:00 (CEST) as a hybrid meeting in Gothenburg, Sweden. The agenda includes adoption of the agenda and report of the 20th session, exchange of information on national and international requirements with presentations on anoise figures in vehicle certificates of conformity versus perceived noise" and on “transportation noise and cardiovascular health”, cross-matrix follow-up discussion, discussion on updating the guidelines of the task force as approved in GRBP-74-03 Rev.1, any other business, and determination of next meeting and provisional agenda.

The Task Force Data Analysis (Sub Group to IWG RD-ASEP) will hold its 12th meeting on Tuesday, 28th April 2026. The agenda includes a review of the meeting schedule with targeted meetings on 19th May, 3rd June, and 9th June, review of database version 3 status and input from Germany on database issues, review of analysis performed, and review of decisions and work for the next meeting.

Proposal to add, modify, and amend Annex 3, Annex 4, Annex 5, Annex 6, Annex 7, Annex 8, Annex 9, and Annex 10, insert Annex 9 (Measurement method to evaluate compliance with the Real Driving Additional Sound Emission Provisions (RD-ASEP)), and add provisions concerning sound emissions, test methods, measurement instruments, vehicle specifications, conformity of production, exhaust systems, compressed air noise, indoor testing, and specific provisions for vehicles equipped with an Automated Driving System (ADS).