UN R13 Supplement 7 (12 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 7 to the 12 series of amendments
Supplement 6 → 7
- What changed
- For full and centre-axle trailers with compressed-air braking, Annex 10 paras 5.1.3. and 5.2.1. now refer to a new diagram 5, not diagram 2.
- The title of diagram 2 no longer names trailers: it now reads “Towing vehicles (except tractors for semi-trailers)”. Diagram 2 also has a new figure.
- Diagram 4A for semi-trailers has a new figure.
- Why
- Friction brakes are used less and less, and in trailers brake pads and linings lose their performance (they “fall asleep”).
- The upper line of the compatibility band limits the maximum brake force in trailers. The proposal was to extend the bands at higher control pressure to allow stronger brakes.
Q1What changed11 changes
New diagram 5 for full trailers and centre-axle trailers, and the diagram 2 title (Annex 10, paras 5.1.3. and 5.2.1.)
For full trailers fitted with compressed-air braking systems, paragraph 5.1.3. now refers to the designated areas in diagram 5 of this annex, not diagram 2. For centre-axle trailers fitted with compressed-air braking systems, paragraph 5.2.1. now derives its two areas from diagram 5, not diagram 2. The new diagram 5 has the title “Full trailers and centre-axle trailers” and refers to paragraph 5 of this annex. The title of diagram 2 changed from “Towing vehicles and trailers (except tractors for semi-trailers and semi-trailers)” to “Towing vehicles (except tractors for semi-trailers)”. Diagram 2 also has a new figure.
New figure for diagram 4A, semi-trailers (Annex 10)
Diagram 4A (Semi-trailers) has a new figure. GRVA replaced the proposed diagrams 4A and 5 with the figures in Annex VII of its session report. Annex VII is based on GRVA-21-59.
Anti-lock braking exemption now also lists diagram 5 (Annex 10, para. 1.1.(b))
Paragraph 1.1.(b) covers towing vehicles and trailers equipped with a compressed air braking system. It applies when they have an anti-lock braking system and fulfil the relevant requirements of Annex 13. For these vehicles, compliance with the unladen compatibility requirements associated with diagrams 2, 3, 4 or 5, as appropriate, is not required. Before, the list was diagrams 2, 3 or 4.
Q2Why it changed
- Proposed by
- Experts from the European Association of Automotive Suppliers (CLEPA)
- Working party
- GRVA, 21st session (January 2025)
Reasons
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 upper line of the compatibility band limits the maximum brake force that may be installed in trailers. Diagrams 2 (for truck and full trailer) and 4A (for semi-trailer) of Annex 10 show this band. The proposal was to extend the compatibility bands at higher control pressure (pm ≥ 500 kPa). It proposed to change diagram 4A for semi-trailers and add a new diagram 5 for full trailers, instead of using 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 (4)
“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.”
“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 as described above.”
The compatibility bands were created more than 50 years ago, when anti-lock braking systems were not available. For towing vehicles and trailers with anti-lock braking systems (ABS), an exemption was implemented: they do not need to fulfil the unladen compatibility bands. The reason is that ABS avoids locking of wheels and keeps the vehicle stable, even with full brake application under all load conditions.
Sources (3)
“The compatibility bands were created more than 50 years ago when antilock braking systems were not available.”
“For towing vehicles and trailers with Antilock Braking Systems (ABS) an exemption has been implemented.”
“These vehicles do not need to fulfill the unladen compatibility bands, because the Antilock Braking Systems will avoid locking of wheels and ensure vehicle stability even with full brake application under all load conditions.”
Document trail
- 2024-11ProposalECE/TRANS/WP.29/GRVA/2025/16Proposal by the experts from CLEPA
- —Amended in sessionGRVA-21-59CLEPA proposal for amendments to the diagrams
- —Working party adoptsECE/TRANS/WP.29/GRVA/21GRVA session report, para. 118 and Annex VII
- 2025-04Sent to WP.29ECE/TRANS/WP.29/2025/57Text 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.16.2026.TREATIES-XI.B.16.13UN depositary notification
Q3Who is affected
Vehicle manufacturer
- For full trailers with compressed-air braking, check TR/PR against diagram 5, laden and unladen (para. 5.1.3.).
- For centre-axle trailers with compressed-air braking, check TR/PR against diagram 5 with the vertical scale multiplied by 0.95 (para. 5.2.1.).
- For semi-trailers with compressed-air braking, use the new diagram 4A figure to check the areas from diagrams 4A and 4B.
Component supplier
- If you supply compressed-air braking equipment for full or centre-axle trailers, check your brake data against diagram 5.
Technical service / Approval authority
- For full and centre-axle trailers with compressed-air braking, assess TR/PR against diagram 5, not diagram 2 (paras 5.1.3. and 5.2.1.).
- For semi-trailers with compressed-air braking, use the new figure of diagram 4A.
- Do not require unladen diagram 5 compliance from compressed-air braked towing vehicles and trailers with Annex 13 anti-lock braking.
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ⓘ This report gives advice only. It is not legal or type-approval advice.
More UN R13 change reports
- 15 series — Supplement 3
- 15 series — Supplement 2
- 15 series — Supplement 1
- 15 series — Base text
- 14 series — Supplement 4
- 14 series — Supplement 3
- 14 series — Supplement 2
- 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 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