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.

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.

Draft minutes of the 74th session of the Informal Working Group WGWT held May 19th, 2026 (9:00–10:00 CET), remotely. Attendance per document WT-74-04. Agenda adopted. Previous meeting minutes of 73rd session (31 March 2026) not uploaded; to be adopted at next session per document WT-74-01. WTPP secretary updated on testing activities status per document WT-74-02. 3PMSF data from one test center pending before sharing anonymised data to WTPP for analysis. JASIC provided completed test data on 3PMSF and Normal tyres. Next meetings: WTPP 35 (28 May 09:00–10:30 CET); WTPP 36 (15 June 09:00–10:30 CET); 75th session (16 June 8:00–9:00 CET); WTPP 37 (02 July 09:00–10:30 CET); WTPP 38 (15 July 09:00–10:30 CET) per document WT-74-02.

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 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.

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.

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.

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.

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’.

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.

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.

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 the workplan 2025–2026 for C1 tyres and test campaign status, preparation of the IWG WGWT status report to GRBP 84th session (September 2026), and identification of next meetings scheduled for 2 July and 15 July 2026.

WTPP has started post-processing activity for the 3PMSF cluster. 90% of test results for normal tyres are expected to be reached by June 2026. WTPP members are working on dataset correction including typos and rounding, and definition of the outliers.

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).

Proposal to amend para. 2.18. to update the year reference in standard F2493 from 24 to 26, amend paras. 6.6. and 6.7. to change “classified” to “categorized”, revise tread depth and void to fill ratio requirements for class C1 special use tyres, restructure requirements for professional off-road tyres with subsections for each class, amend Annex 3 para. 4.2.2. to correct the measurement unit of coefficient K1 to dB(A), amend Annex 3 Appendix 1 Part 2 item 3.1. to update the ISO 10844 year reference from 2014 to 2021, and amend Annex 7 Appendix 3 Item 5 to enable SRTT weighted average to be reported for each candidate in the test results table.

Proposal to amend para. 2.18. to change the reference year from 24 to 26 for standard F2493, add new para. 2.21. defining “road legal race tyre,” add new para. 4.2.8. requiring the inscription “RLR” for road legal race tyres, insert new footnote 12 on marking height, renumber current footnote 12 to footnote 13 and amend its text, amend para. 5.4.1. to reference footnote 13, add new para. 6.9. establishing requirements for road legal race tyre classification, add new item 4.3. to Annex 1, amend para. 6.7. to change “classified” to “categorized,” amend Annex 3 para. 4.2.2. tables to change K1 unit from C to dB(A), amend Annex 3 Appendix 1 Part 2 item 3.1. to update ISO10844 reference from 2014 to 2021, and amend Annex 7 Appendix 3 Item 5 table to enable reporting of SRTT weighted average for each candidate.

UN R117 establishes test procedures ensuring reliability, repeatability and reproducibility of results through standard reference test tyres manufactured by Manufacture Francaise des Pneumatiques Michelin in accordance with ASTM International standards. In 2024, the Russian Federation’s technical service was officially refused supply of these tyres due to export sanctions. The Russian Federation contends this refusal constitutes discrimination against a Contracting Party to the 1958 Geneva Agreement and calls on WP.29 to assess this discrimination and explain to the manufacturer its role in implementing the Agreement within the UN system.

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.