This document proposes a new UN Global Technical Regulation (UN GTR) for measuring brake particle emissions from Heavy-Duty Vehicles (HDVs). The GTR establishes a harmonised laboratory methodology covering the Worldwide Harmonised Heavy-Duty Vehicles Brake Cycle (WHBC), test system requirements, and measurement protocols for particulate matter (PM) and particle number (PN) emissions.

Key substantive elements include:

- Scope covering M₂–M₃, N₂–N₃, and O₃–O₄ category vehicles with friction braking systems
- Detailed specifications for brake dynamometer systems, enclosure design, sampling tunnel geometry, and cooling air conditioning
- Definition of the WHBC comprising three segments (urban, rural, motorway) with 246 brake events over 20,353 seconds and 271 km
- Brake bedding procedure (six consecutive WHBC cycles) followed by a single WHBC emissions measurement section
- Requirements for PM₁₀ and PM_2.5 gravimetric sampling using cyclonic separators and filter-based collection
- Requirements for TPN₁₀ and SPN₁₀ measurement using dilution systems and particle number counters with specified PCRFs
- Detailed quality checks including speed violations, brake event count verification, and kinetic energy dissipation tolerances
- Comprehensive calibration requirements for dynamometer, flow measurement, weighing equipment, and sampling/measurement devices
- Test output specifications including Event-Based, Time-Based, Mass Measurement, and Test Report files

The regulation applies a friction braking share coefficient to convert reference emission factors from the tested brake to final emission factors applicable to the vehicle.

Task Force 4 has completed revisions to GTR 24 concerning electro-mechanical calipers and proposes to include them in Amendment 3.

TF 3c addressed brake emission of replacement parts. Proposed amendments include clarification that surface heat-treated discs fall under “other” category, refinement of “Brake Emissions Family Parent” definition, and addition of new appendix to UN Regulation No. 179 Annex 2. Data sharing agreement established: front-to-rear axle emission ratio, brake force distribution, and vehicle electrification type will be shared with aftermarket operators. Two approaches for aftermarket applicants: use vehicle-specific data through benchmarking or bilateral agreements, or apply default values from Tables 5.4 and 5.5. Testing revealed up to 30% variation within friction-couple families. Safety factor application when using actual c-factor values remains under discussion, with final decision expected before October.

Proposal to amend UN R179 following GRPE-94-15e:

• Include supplements on automated vehicle definitions and OICA proposals on family members with higher wheel load but lower wheel load times c-factor ratio,
• Clarify wheel load and vehicle mass definitions for different tests,
• Add wheel load distribution for light commercial vehicles with fully laden mass between 3.5 and 5 tonnes,
• Redefine brake assembly to allow brake calliper reuse if in technically suitable condition,
• Optionally omit cooling air adjustment if temperature requirements are fulfilled,
• Require three emission measurement sections instead of one for type approval with arithmetical average reported,
• Clarify energy calculation for vehicles with limited speed,
• Harmonize reporting requirements including units and decimals,
• Define normalized flows,
• Include transitional provisions stating that vehicle types with existing valid type approvals issued before entry into force of supplement 2 need not undergo new type approval testing.

Task Force 5 progressed toward GTR adoption planned for GRPE 95th session in 10/2026. JRC endurance braking tests conclude 07/08/2026. A small round robin exercise with six participants tests three airflow settings to finalize bracketed values. Key updates include maximum sampling probe length of 1.35m, PM10 probe positioning on outside streamline for bent layouts, and probe distance reduction from 100mm to 70mm. Proposal to delete the Disc or Drum Metallurgy for Brake Groups section. Final GTR text requires PMP comments by 22/07/2026, with layout decisions by 16/07/2026. UNR drafting based on UN R179 skeleton has commenced with significant work required.

Task Force 3b addresses vehicles with limited speed by introducing a new Appendix 3 in Annex 4 to calculate adjusted cycles when vehicle maximum speed is lower than the WLTC-Brake cycle. The proposal modifies brake corner emissions family testing to allow vehicles with limited speed to be included in families with standard vehicles, with emission factors calculated from parent family factors or measured on adjusted cycles. Amendments address c-factor measurement, cycle-adjusted brake events, kinetic energy dissipation tolerances, and report file specifications.

This document proposes a new UN Regulation on uniform provisions concerning approval of non-original and identical replacement brake parts regarding particulate emissions. The regulation applies to laboratory measurement of brake emissions from non-original replacement brake pads, linings, discs, and drums for vehicles of categories M₁, N₁, and N₂ originating from vehicles with type approval under Regulation No. 179. Approval requires emission factors to comply with specified limits based on vehicle category and powertrain technology. The regulation establishes brake emissions families based on characteristics including calliper type, vehicle axle location, friction material formulation, brake disc or drum material, disc surface form, friction material surface area, and drum diameter. Testing procedures, conformity of production requirements, marking and packaging specifications, and approval extension procedures are detailed.

Proposal to insert new paras. 3.3.29. to 3.3.33. defining “Semi-Metallic-Organic,” “Low-Steel-Organic,” “Non-Asbestos-Organic,” and “Low-Steel-Non-Organic” friction materials and “Pad area,” amend Annex 2 title to read “Annex 2 Communication,” insert a new footnote to Annex 2, and insert a new Annex 2 – Appendix containing a list of vehicle data for UN Regulation No. [XXX] approvals including vehicle type description, brake linings and discs specifications, vehicle test mass, maximum speed, tyre dimensions, brake circuit configuration, and brake specifications.