UN R13 Supplement 2 (14 series) · UNECE Regulation No. 13 (ECE R13) — Uniform provisions concerning the approval of vehicles of categories M, N and O with regard to braking.
UN R13 — Supplement 2 to the 14 series of amendments
Supplement 1 → 2
- What changed
- This supplement adds a new Diagram 5 for full trailers and centre-axle trailers to Annex 10.
- Paragraphs 5.1.3. and 5.2.1. of Annex 10 now refer to diagram 5 instead of diagram 2.
- The words “and trailers” and “and semi-trailers” are removed from the title of Diagram 2, and the figures of Diagrams 2 and 4A changed.
- Why
- The proposal aimed to resolve the problem of decreasing trailer brake performance caused by brake pads and linings “falling asleep”.
- The proposal says that the upper line of the compatibility band limits the maximum brake force that may be installed in trailers.
- The proposal aimed to allow stronger brakes with higher brake forces and a higher safety margin, to compensate for the possible loss of brake performance.
Q1What changed11 changes
New diagram 5 for full trailers and centre-axle trailers (Annex 10, paras. 5.1.3. and 5.2.1.)
This supplement adds a new Diagram 5 with the title “Full trailers and centre-axle trailers” (see paragraph 5 of this annex). Paragraph 5.1.3. now refers to the designated areas in diagram 5 instead of diagram 2. Under paragraph 5.2.1., the two areas are now derived from diagram 5 instead of diagram 2, by multiplying the vertical scale by 0.95. In both paragraphs, the pressures between 20 and 750 kPa and the laden and unladen states of load stay the same.
Title of Diagram 2 (Annex 10)
The title of Diagram 2 now reads “Towing vehicles (except tractors for semi-trailers)”. Before, it read “Towing vehicles and trailers (except tractors for semi-trailers and semi-trailers)”. The reference to paragraph 3.1.5.1. of the annex stays the same.
Figures of Diagrams 2 and 4A (Annex 10)
This supplement changes the figures of Diagram 2 and Diagram 4A. Diagram 4A is for semi-trailers (see paragraph 4. of this annex).
Unladen exemption for vehicles with an anti-lock braking system (item (b) of Annex 10, para. 1.1.)
Item (b) of paragraph 1.1. now lists diagrams 2, 3, 4 or 5, as appropriate, instead of diagrams 2, 3 or 4. Item (b) is one of the exceptions for vehicles that are equipped with an anti-lock braking system and fulfil the relevant requirements of Annex 13. For towing vehicles and trailers with a compressed air braking system, compliance with the unladen compatibility requirements of these diagrams is not required. For all load conditions, the braking rate rule (between 20 kPa and 100 kPa or the equivalent digital demand value) stays the same.
Q2Why it changed
- Proposed by
- Experts from the European Association of Automotive Suppliers
- Working party
- GRVA, 21st session (January 2025)
Reasons
The proposal aimed to resolve the problem of decreasing trailer brake performance caused by brake pads and linings “falling asleep”.
Source
“to resolve the problem of decreasing trailer brake performance caused by brake pads and linings “falling asleep””
The number of trucks with strong endurance braking systems is increasing, and electrification will bring more highly efficient energy recuperating systems. As a result, friction brakes are used less and less. Depending on the use of the commercial vehicle, brake pads and linings often do not reach the temperature that they need for optimum brake performance. In trailers in particular, pads and linings lose their performance (they “fall asleep”) and need to be replaced although they are not worn out.
Sources (5)
“The number of trucks with strong endurance braking systems is increasing since a long time.”
“With increasing electrification of vehicles more highly efficient energy recuperating systems will be installed in future.”
“This leads to the situation that the use of friction brakes is more and more reduced.”
“brake pads and linings often do not reach a temperature that is needed for the development of optimum brake performance”
“In particular in trailers a loss of brake force is experienced due to brake pads and linings that lose their performance - they “fall asleep” and need to be replaced although they are not worn out.”
The maximum brake force that may be installed in trailers is limited by the upper line of the compatibility band. At the time of the proposal, diagram 2 (for truck and full trailer) and diagram 4A (for semi-trailer) of Annex 10 showed this band.
Sources (2)
“the maximum brake force, which may be installed in trailers is limited by the upper line of the compatibility”
“as currently shown in diagrams 2 (for truck and full-trailer) and 4A (for semi-trailer) of Annex 10”
The proposed solution extends the compatibility bands at higher control pressure. It changes diagram 4A for semi-trailers and adds a new diagram 5 for full trailers, instead of the use of diagram 2 for towing vehicles. This allows stronger brakes with higher brake forces and a higher safety margin, to compensate for the possible loss of brake performance.
Sources (2)
“Extension of the compatibility bands at higher control pressure (pm ≥ 500 kPa) by modification of diagram 4A for semitrailers and adding a new diagram 5 for full trailers instead of using diagram 2 for towing vehicles.”
“stronger brakes with higher brake forces and higher safety margin to compensate for the possible loss of brake performance”
Document trail
- 2024-11ProposalECE/TRANS/WP.29/GRVA/2025/16Proposal by experts from the European Association of Automotive Suppliers
- —Amended in sessionGRVA-21-59Proposal for amended diagrams 4A and 5, published after the session
- —Working party adoptsECE/TRANS/WP.29/GRVA/21GRVA session report, para. 118 and Annex VII
- 2025-04Sent to WP.29ECE/TRANS/WP.29/2025/59Text that GRVA sent to WP.29 and AC.1
- 2025-06WP.29 adoptsECE/TRANS/WP.29/1186Adopted at the 196th session (session report, para. 111)
- 2026-01-11In forceC.N.18.2026.TREATIES-XI.B.16.13UN depositary notification
Q3Who is affected
Vehicle manufacturer
- For full trailers and centre-axle trailers, check the braking rate TR/PR against the new diagram 5 (paragraphs 5.1.3. and 5.2.1.).
- For semi-trailers, compare your braking rates with the changed figure of Diagram 4A.
- For towing vehicles other than tractors for semi-trailers, compare your braking rates with the changed figure of Diagram 2.
Component supplier
- For full trailers and centre-axle trailers, check that your braking systems can meet the new diagram 5.
Technical service / Approval authority
- When you test full trailers and centre-axle trailers, use diagram 5 instead of diagram 2 (paragraphs 5.1.3. and 5.2.1.).
- Use the changed figures of Diagram 2 and Diagram 4A in your tests.
- Include diagram 5 when you apply the item (b) exemption from the unladen compatibility requirements.
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ⓘ This report gives advice only. It is not legal or type-approval advice.
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- 15 series — Base text
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- 14 series — Supplement 1
- 14 series — Base text
- 13 series — Supplement 7
- 13 series — Supplement 6
- 13 series — Supplement 5
- 13 series — Supplement 4
- 13 series — Supplement 3
- 13 series — Supplement 2
- 13 series — Supplement 1
- 13 series — Base text
- 12 series — Supplement 9
- 12 series — Supplement 8
- 12 series — Supplement 7
- 12 series — Supplement 6
- 12 series — Supplement 5
- 12 series — Supplement 4
- 12 series — Supplement 3
- 12 series — Supplement 2
- 12 series — Supplement 1
- 12 series — Base text
- 11 series — Supplement 23
- 11 series — Supplement 22
- 11 series — Supplement 21
- 11 series — Supplement 20
- 11 series — Supplement 19
- 11 series — Supplement 18
- 11 series — Supplement 17
- 11 series — Supplement 16