The 56th PMP session convened online on 7 May 2026 with approximately 70 participants. Meeting minutes from 13 March 2026 were accepted. PMP agreed on a joint neutral template for all task forces. TF3a discussed cooling air adjustment, temperature criteria, and vehicle emission factors, with proposals requested by end of May 2026. TF3b will discuss family building and speed-limited vehicles. TF3c presented brake replacement parts activities. TF4 prepared work package B on electromechanical brakes and requested feedback by end of May 2026. TF5 reported progress on GTR on HD brake particle emissions with test campaigns planned. The next meeting is expected end of June or beginning of July 2026.

PMP TF 3a is consolidating and updating UN R179 and GTR 24 through weekly web-meetings organized by JRC with 30+ participants. Over 50 topics have been identified and categorized by priority. Key issues include aligning Type Approval and Conformity of Production testing procedures, harmonizing cooling air adjustment requirements, clarifying vehicle c-factor calculations, adding definitions for light-duty vehicles exceeding 3.5 tonnes, and addressing test wheel load per GRPE-94-15e. The task force is preparing track changes versions and supporting documentation for major changes.

Task Force 4 addresses brake system development towards dry brakes, specifically electromechanical brakes. Current methods to determine friction brake torque available for hydraulic systems are not all applicable for dry systems. Task Force 4 targets defining a pressure-based equivalent method for electromechanical brake systems and reviewing document validity for electromechanical braking systems. Work Package B completed text document review with proposed changes due end of May 2026. Work Package A discusses two alternative approaches for c-factor calculation: clamping force based and recuperated energy based, with verification tests planned by end of June 2026.

Proposal to amend UN GTR 24 (Laboratory Measurement of Brake Emissions for Light-Duty Vehicles) by clarifying requirements for electromechanical brakes and dry brakes, modifying test procedures, updating definitions and technical specifications, revising cooling airflow adjustment methodologies, refining PM and PN measurement protocols, and adjusting calibration intervals and quality control procedures.

The PMP webex meeting scheduled for 7 May 2026, 12:00-14:30 CET will review meeting minutes from 13.03.2026, provide an overview of amendments to Brakes GTR 24 and UN R179 covering layout and testing topics, vehicle limited speed, brake replacement parts, and electromechanical brakes, discuss GTR HD brakes, and address any other business.

The PMP session discussed revisions to the group’s terms of reference to address overlapping technical issues with GTR 24, UN R179, and replacement parts regulations. Three task forces were proposed: TF3a on layout and testing, TF3b on speed-limited vehicles, and TF4 on electromechanical brakes. Topics included non-original brake parts regulations, UN R179 amendments for new vehicle categories, and GTR heavy-duty brake particle emissions standards. The next meeting was scheduled for end of April 2026.

Proposal to transpose GTR 24 on laboratory procedures for the measurement of brake particle emissions into a UN Regulation. An informal document amending this proposal is under development.

Figure 12.1 shows the indicative setup of the PM sampling system with sampling plane, sampling nozzle, PM sampling probe, PM cyclonic separator, PM sampling line, PM filter holder, PM sampling filter, mass or volumetric flow measurement, pump, and flow controller. Figure 12.3 shows the indicative setup of the PN sampling and measurement system with sampling plane, sampling nozzle, PM sampling probe, flow splitter, PN particle transfer tube, PN cyclonic separator, HEPA-filtered inlet for dilution air, dilution stage, Volatile Particle Remover, Particle Number Counter with internal flow controller and mass or volumetric flow measurement, and pump.

Proposal to add quality checks for applied brake torque to GTR 24, including methods for calculating Brake Torque Rising Criterion, Brake Torque Maximum Criterion, and Brake Torque Stability Criterion based on signals with frequency of 250 Hz or faster, to be recorded in Event-Based Files and reported in summary table 13.6, and to add signal filtering requirements to chapter 5.4 specifying a second order filter with cut-off frequency between 25% and 50% of the lower sampling or recording frequency to fulfill Nyquist-Shannon sampling theorem.

Proposal to establish quality criteria for applied brake torque datasets at 250 Hz sampling rate by calculating rising criterion, maximum criterion, and stability criterion for each brake event. Rising criterion measures time to reach ninety per cent of nominal brake torque and overshoot at brake event start. Maximum criterion calculates maximum brake torque weighted by nominal specific kinetic energy. Stability criterion reports average brake torque and root mean squared error weighted by nominal specific kinetic energy. Results show variation across laboratories. Further investigation necessary for different brake types, threshold definition for failed brake events, and inclusion of method and criteria reporting in event based file.

PM samplers must sample continuously until 10 seconds after the end of the WLTP, as particles require 10 seconds to reach the filter after the last brake event. PN calculation does not completely cover all PN of the trips’ last brake event due to time delay and smoothing during the calculation period. Based on ILS data, extending the TBF export by 5 seconds would result in maximum emission factor differences of approximately 0.35 percent, estimated below 1 percent overall influence.

ILS 3 Findings and GTR 24 Updates addresses improvements to the Particle Measurement Programme. References to three-probe layout and smaller duct diameters are deleted; duct inner diameter is defined as 190–225 mm. A column defining numbers of decimals is added to Table 8.1. Bedding and emissions measurement sections shall use new parts. Temperature requirements at filter holder are clarified to remain above 15°C. Requirements on decimal places are added throughout Tables 13.1, 13.3, 13.4, 13.5, and 13.6. Table 13.6 now counts from 1 to 274. Unit notation is harmonized. Signal filtering requirements are added to Chapter 5.4. Various requests are rejected, including repositioning sampling nozzles and probes, PM₁₀ probe positioning, and OEM-declared threshold pressure values.

PMP Task Force 5 is working on HDV Brake Dyno Layout and HDV Brake Test Cycle. A GTR proposal is planned by the end of 2025.

Proposal to amend para. 8.2.(k) to require calculation of average drag torque over a 5 s period during constant speed phases rather than acceleration phases, amend para. 8.2.(d) to clarify brake run-out measurement procedures for drum brakes including verification measurement at final assembly, amend para. 8.2.(e) to specify assembly procedures for drum brake testing, insert para. 12.1.2.3.(c) to clarify flow measurement device calibration requirements for PM sampling, and insert para. 12.2.3.2.(c) to clarify flow measurement device calibration requirements for PN sampling, based on ECE/TRANS/WP.29/GRPE/2025/6.

This document evaluates the AIP dustIN multisampling PM10 system using an ILS-3 brake on a BMW X5 tested across the WLTC cycle with brake cooling airflow at 500, 1000, and 1500 m³/h. Testing involved six tests per flowrate comprising regular runs with repetitions. Deviations between multisampler and single sampling were less than 5 percent, covered by measurement uncertainty and partly caused by different sampling positions. No significant loss impact by the dustIN multisampler was identified. A PM2.5 campaign is currently running.

Proposal from the Particle Measurement Programme informal group to improve the text and test protocol.

• Additional chassis dyno quality criteria
• Threshold pressure calculation method
• Table 5.3
• Annex C clarifications and adaptations

Proposal from the Particle Measurement Programme informal group to improve the text and test protocol. A version of this document with tracked changes is available.

Proposal to introduce a vehicle-specific non-friction braking measurement procedure, definition of brake emission families and other changes with the aim of improving the overall protocol.

Proposal as adopted by GRPE for consideration during the June 2024 WP.29 session.

Revision prepared after the 90th session based on GRPE decisions during the session.

• Equivalency of Method B and Method D (CAN)
• Statement to Brake Particle filters
• Vehicle selection / Family building
• Fuel Cell vehicles

Revised technical report to align with the work on Amendment 1.

Regulatory and Technical Differences Between HDV and LDV Braking Systems and Brake Emissions.

• Statement on Brake Particle filter testing
• Correlation of Method B and Method D (CAN)
• OICA input to ILS-3
• Aftermarket and Original replacement parts – definitions

Proposal from the PMP informal group to introduce a vehicle-specific non-friction braking measurement procedure, definition of brake emission families and other changes with the aim of improving the overall protocol.

Comments on

• Overview and priorities
• Technical details to ANNEX-C and GTR-24
• Implementation of multiple sampling
• GTR-24 Testing boundaries for Light weight discs (see separate file)
• Correlation: WLTP Brake / WLTP-Exhaust
• Friction share family building
• Axle specific friction share coefficients.

PMP informal group report on non-exhaust particle emissions developed under the brake emissions GTR project.

Proposal concerning the annex on the procedure to determine vehicle-specific friction-braking share coefficients.

• Non-friction energy share methods
• Status of informal document Annex-C
• Status of informal document Annex-C – ToDo’s
• Accuracy of Pressure Transducers and Calibration protocol
• Effect of 0.5 bar cut-off criteria
• Calculation of energy weighted c_p: WLTP-Brake vs. Trip 10
• Data comparison Method B
• Correlation: WLTP Brake / WLTP-Exhaust
• Correlation plot c-Factor WLTP Brake Full vs Trip 10
• Alternative methods
• Development/Homologation Flow

Proposal for the annex concerning the procedure to determine vehicle-specific friction braking share coefficients.

Proposal to establish harmonized provisions for the measurement of brake wear particle emissions.

Updated proposal for the new GTR on laboratory measurement procedures for brake particulate emissions from the PMP informal group. This document is also available with tracked changes in pdf version and .docx format.

Report on the background and development of the text for a new UN GTR on laboratory measurement procedures for brake particulate emissions.

Proposal from the PMP informal group to establish harmonized provisions for the measurement of brake wear particle emissions.