The subgroup on UN R51 and UN R138 met on 14 January 2026 to review comments on outcome documents. Switzerland’s sentence in 3.5. was retained for clarification. JASIC’s definition of EES footnote was changed to reference GRB-68-03. Transitional provisions remained unchanged with a new item added for Annex 1, Appendix 1. Agreement was reached on 6 dB allowance in Annex 7 paragraph 3.4. and 3 dB for three specific cases. A draft paragraph for GRB-68-03 justification will be submitted by email. Switzerland’s proposal SG-13-05-2025-07-30 will serve as basis. GRBP-82-39 includes examples for active systems generating EES and creation of part B for electric vehicles. Work on RD-

Proposal to amend GRBP/2026/4. Amendments to UN Regulation No. 51 include updates to the Table of Symbols in paragraph 2.24; new definitions for Active Sound Source, Enhanced Exterior Sound (EES), and Vehicle Master Control Switch; specifications for EES operation requiring driver intentional action and default deactivation; sound limits complying with UN-Regulation No. 138 below 20 km/h and this Regulation from 20 to 80 km/h; transitional provisions allowing extension of existing approvals for 24 months; modifications to Annex 7 control ranges, anchor points, and slope calculations for electrically propelled vehicles; and updates to Annex 1 and Annex 3 regarding EES systems. GRB-68-03 commitment to add EES guidance document is confirmed.

The secretary reported on C1 tyre testing activities. The Netherlands and Germany noted potential delays in Normal tyre testing at high temperature by end of March due to temperature conditions. The co-chair presented a status report for GRBP’s 83rd session, which the group approved. Future meetings are scheduled for February through April.

The GOIE on Tyre Noise Level Alignment in UN R117 targets reducing dispersion of measurements for tyres of Class C1 and C2 and investigating possibility to develop a test method with an SRTT as reference. An intermediate report will be presented to GRBP in September 2026, with a Working Document proposing evolution of the test method by September 2027. Five meetings have been held with 13 test centres from France, Japan, Netherlands, Spain and ETRTO. Eight of thirteen test centres have completed tests on 15 C1 and 5 C2 Japanese market tyres, with completion targeted for mid-2026.

Proposal to amend paragraph 2.18. to update Standard Reference Test Tyre definitions to ASTM International standards: E1136-19 for SRTT14, F2493-24 for SRTT16, F2872-25 for SRTT16C, F2871-25 for SRTT19.5, F2870-23 for SRTT22.5, F3678-25 for SRTT19.5 siped, and F3677-23 for SRTT22.5 siped. Also amend paragraph 12.21. to accept existing type approvals and grant extensions to class C₃ tyres using either SRTT19.5 or SRTT22.5 before 1 September 2028, and use SRTT19.5 siped or SRTT22.

Proposal to supersede document GRBP/2026/4 intended to introduce a “default mode”, to specify requirements to be applied to the emission of Enhanced Exterior Sound (EES), with corresponding transitional provisions, and to draw a limit curve to introduce electric vehicles and hybrid electric vehicles that can be propelled without an internal combustion engine operating in the scope of ASEP (Annex 7).

The RD-ASEP informal group met in February 2026 in Geneva. The Analysis Task Force requested additional data on hybrids, CVT transmissions, and battery electric vehicles. The Editing Task Force addressed copyright issues with UN and ISO Secretariats, determining that current document practices continue unchanged. The group clarified that RD-ASEP development focuses on measurement procedures for real driving conditions and noise emission limits under full and partial load, not establishing a new regulatory phase.

The RD-ASEP informal group met in Brussels. Officers and representatives from eleven contracting parties and four NGOs were present. The group discussed copyright approval requirements for UN website materials. A February 2026 meeting with UNECE and ISO secretariats will address incorporating third-party standards into UN regulations. The Data Analysis Task Force reported on ESE in ICE vehicles and data limitations. Discussions covered vehicle control ranges, CVT handling, and vehicle category applicability. An issues list was established for draft regulatory text. The next meeting is scheduled for April 14-16, 2026 in Berlin.

Proposal to amend Annex 3 of UN Regulation No. 51-02, paragraph 3.1.2.3.2.3, third paragraph, to require gear shifts beginning with (x/n) continue in all gears at which rated engine speed is reached immediately before the rear of the vehicle passes line BB’, rather than being completed in gear X only, based on WP.29-196-08 and WP.29-197-11 findings of non-compliance with permissible sound level requirements for category N₃G vehicles during state control testing.

ETRTO measurement uncertainties reduction efforts for UN R117 rolling sound emission test methods are progressing through outdoor and indoor Round Robin tests. Eight of thirteen outdoor test centres have completed tests for C₁ and C₂ tyres; remaining centres anticipate completion by mid-year. Indoors, two of six ETRTO test centres completed tests with others expected finished by mid-year. An intermediate report with available data will be presented in September 2026, full results postponed to February 2027, and the Working Document with test method evolution now expected in September 2027 instead of February 2027.

Consolidation in Supplement 11 includes: clarification of Verification/Adjustment and editorial corrections with transitional provisions (GRBP/2025/20 with GRBP-82-07); correction of Tyre Road Sound Measurement for Indoor-Testing (GRBP-82-22); introduction of ASEP in Annex 7 for BEVs and HEVs (GRBP/2026/4 with GRBP-83-xx); update of ISO standards in Annex 3 and Annex 8 (GRBP/2026/5 with GRBP-83-xx); and reference for Power Definition regarding new UN R177 (GRBP/2026/13). The consolidated version of Supplement 11 is to be submitted to the 199th WP.29 in June.

ISO 362-3:2022 specifies an engineering method for measuring pass-by sound level of a vehicle under controlled indoor conditions using a semi-anechoic chamber. The 2022 edition incorporates technological advancements and improves usability and accuracy of the measurement procedure. Improvements include additional microphones, tire temperature correction harmonized with UN R51.03, clarified indoor room qualification criteria, and normalized torque influence equation. Transitional provisions propose accepting ISO 362-3:2022 for all approvals from entry into force of Supplement 11, while ISO 362-3:2016 remains accepted for five years thereafter.

Proposal to supersede GRBP/2025/28, consolidating amendment proposals from GRBP/2025/28, GRBP-82-27, GRBP/2026/6, and GRBP-83-20-Rev.2. Changes include moving tyre abrasion provisions to a separate UN Regulation, deleting paragraphs 5.7 to 5.10 and Annex 10, updating ASTM standard references to F2872-25, F2871-25, and F3678-25, amending Annex 5 part (b) paragraph 1.1.1., and deleting paragraph 2.21. defining abrasion performance terms.

Proposal to amend Annex 5, part (B) of UN R117. Changes include replacing “Average Deceleration (AD)” with “braking force coefficient (BFC)” terminology throughout paragraphs 2.2.2.1., 2.2.2.7.1., 2.2.2.7.2., and 2.2.2.7.3. Paragraph 2.2.2.3. is amended to clarify terminology regarding vertical static test load and load capacity. Paragraph 2.2.2.7.4. is deleted. Paragraphs 2.2.2.7.5. through 2.2.2.8.4. are renumbered and amended to align the wet grip test method for C2 and C3 tyres with changes made to the passenger car test method and ISO 15222:2025.

CLIV is developing a new UN Regulation for vehicle categories M1, M2, M3, and N1 in Phase 2. The draft regulation requires visual and audible external warnings upon detection of a child left in a vehicle. Visual warnings use direction indicator lamps flashing in SOS morse code pattern for at least 15 seconds, then off for no more than 30 seconds, repeating for at least 10 minutes. Audible warnings must exceed 60dB(A) following the same timing pattern. The IWG requests guidance on potential amendments to UN R48, UN R28, and UN R165.

The Task Force Data Analysis completed data revision for RD-ASEP specifications, identifying errors and inconsistencies. The document lists considerations for database improvements, including updating limits to UN R51.03 phase 3, clarifying vehicle reference speed definitions, correcting reported loads exceeding 100%, selecting correct parameter tables, and addressing gear shifting detection. Additional recommendations involve determining acceptable factor x ranges, resolving minimum dynamic calculation inconsistencies, increasing va_MAX validity thresholds, and reconsidering AVAS term applicability for hybrid vehicles.

The Data Analysis task force met with limited participation from Japan, Netherlands, and the pilot. The group reviewed corrections made to vehicle load issues and reference speeds. They determined that corrections to PMR and L_urban calculations would be too time-consuming without adding substantial benefit and are not currently used by the model. A proposal for generic reference acceleration determination requires further assessment, as initial analysis indicates the formula overestimates acceleration potential. The data review process should be closed, so the official work with the database can start.

The Task Force Data Analysis has almost completed data revision for RD-ASEP specifications, identifying inconsistencies and proposing corrections. Key considerations include: updating database limits to UN R51.03 phase 3, clarifying vehicle reference speed interpretation, correcting reported loads exceeding 100%, selecting correct parameter tables, defining run interdependency, strengthening tyre rolling sound specifications, resolving minimum dynamic calculation inconsistencies, improving gear shifting detection, reconsidering sound level maximum basis, increasing performance validity threshold, accepting runs outside control range with manufacturer agreement, and reviewing AVAS term application for hybrid vehicles.

The Task Force Data Analysis agenda covers welcome and agenda adoption; review of meeting schedule with sessions scheduled through June 2026; discussion of actions and considerations for the IWG and Editing group; review of vehicle review list Version 19; database status and release timing; decisions and work for subsequent meetings; and closing remarks.

During the 19th session

• OICA commented on LEON-T project reports regarding tyre and powertrain noise contributions.
• The European Environment Agency presented findings on transport noise exposure affecting over 100 million Europeans.
• Norway presented a proposed 95 dB(A) noise limit for stationary vehicles under UN R51.
• France proposed amending UN R28 to introduce soft audible warning devices for M and N category vehicles.
• The task force suspended its cross-matrix activity and postponed discussion of L-category vehicles to the next session.

The agenda covers the 13th session of the Informal Group for Real Driving Additional Sound Emission Provisions, held June 10-12, 2026, in Gothenburg, Sweden. Topics include RD-ASEP Terms of Reference from GRBP 78th Session (GRBP-78-13), R51 matters including procedural update (GRB-68-03), Analysis Task Force Report, Editing Task Force Report, R51.04 Issues List Review, draft R51.04 text review, Inside Boundary Condition discussion, and Outside Boundary Condition discussion. The next meeting is scheduled for August 31–September 1 in Geneva, Switzerland.