UN R13 Supplement 2 (15 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 15 series of amendments
Supplement 1 → 2
- What changed
- New paragraph 5.2.2.26. sets requirements for the dynamo function of e-axle trailers, such as a 22 kW retardation power limit for O3 and O4 trailers.
- For the static parking brake requirements, a park lock device may now be used, alone or with means acting on the braking surfaces (para. 5.2.1.10.).
- Except where no suitable interface exists, brake demand values must also be readable through an electronic vehicle interface, for example the OBD port (para. 5.1.4.6.2.1.).
- Why
- The provisions for trailers with e-axles (dynamo function) aim to increase the efficiency of these vehicles.
- CITA proposed the live reading of brake demand values during periodic technical inspections, for more accurate assessments of brake system performance.
- The proposal on the park lock device aimed at allowing for the type approval of park locks.
Q1What changed55 changes
E-axle trailers: scope and definitions (paras 1.2.6., 2.57. to 2.59., Annex 2)
This Regulation does not cover e-axle trailers with e-axles providing electric propulsion and/or incorporating an electric regenerative braking system (new para. 1.2.6.). An “e-axle” is now defined as an axle mounted to a vehicle of category O generating electrical energy and/or providing electrical propulsion (para. 2.57.). An “e-axle trailer” is a trailer of category O with at least one e-axle, “while the trailer is not designed to move on its own” (para. 2.58.). The “Dynamo function” of an e-axle trailer is the capability of a trailer “to provide for the conversion of vehicle kinetic energy into electrical energy without affecting the forces developed by the braking system” (para. 2.59.). A dynamo function is not part of the braking system and not considered as a brake. Annex 2 has a new item 14.18. on whether the trailer is equipped with an e-axle having a dynamo function.
Requirements for the dynamo function of e-axle trailers (paras 5.2.2.26. to 5.2.2.26.5.)
Trailers of Category O1 and O2 with a dynamo function must not be approved under this Regulation until uniform technical provisions are agreed. For the complete trailer of Category O3 and/or O4, the dynamo function must not provide a retardation power of more than 22 kW. The owner’s manual must state that, in a multiple trailer combination of Category O3 and/or O4, the 22 kW limit applies to “the sum of the retardation power of all dynamo function devices of the combination”. If the dynamo function can generate a braking rate of more than 0.04 per wheel, it must be controlled so that it “does not cause wheel locking and has no critical impact on the vehicle behaviour”. Its operation must be assessed according to Annex 18, and O3 and O4 trailers must meet Annexes 13 and 21 with it enabled. For a dynamo function according to paragraph 5.2.2.26.2., paragraph 5.2.2.26.5. sets comparison tests with and without the dynamo function active.
E-axles and the dynamo function in Annexes 4, 5, 10, 19, 20 and 21
In Annex 4, the e-axle functions of an e-axle trailer (para. 1.4.1.2.2.) and a dynamo function (para. 1.7.1.3.) must not be used during brake applications. Under Annex 10, the retarding force of a dynamo function must also not be taken into consideration when the vehicle performance is determined. In the Annex 19 tests of paragraphs 4.5.1.5. and 4.5.1.6., any dynamo function must be disengaged, like any endurance braking system. In Annex 5, for certain vehicles as specified in the ADR, the switch-off and anti-lock control rules for endurance braking systems also apply to e-axles. An e-axle with a dynamo function is excluded if the prevention from locking the wheel(s) is not based on the anti-lock braking system. E-axles are added to the schematic diagram items of Annex 19, Appendices 5 and 7, and the axle arrangement items of Annexes 20 and 21.
Brake demand values through an electronic vehicle interface (paras 2.60., 5.1.4.6.2.1., 12.9.8.)
Except where no suitable interface exists, the brake demand value(s) must now also be readable through an electronic vehicle interface (para. 5.1.4.6.2.1.). The OBD port is given as an example of the interface, and the reading uses an off board electronic device. The vehicle manufacturer must now also describe how to access those values, not only how to display them. New paragraph 2.60. says that the “Electronic vehicle interface” provides the access to real time parameters of the braking system specified within this regulation. New paragraph 12.9.8. sets a time limit of 24 months after the entry into force of Supplement 2 to the 15 series. Until that time, Contracting Parties applying this Regulation can continue to grant or extend 15 series approvals without the amendments to paragraph 5.1.4.6.2.1.
Park lock device in the parking braking system (paras 5.1.4.5.4., 5.2.1.10.)
For the static parking brake requirements of Annex 4, paragraphs 2.3.1 and 2.3.2, the parking braking system may now use a park lock device. The device may act as an alternative to or in combination with means acting on the braking surfaces (para. 5.2.1.10.). The park lock device must consist of components of an adequate strength and give equal effectiveness compared to layouts purely acting on the braking surfaces. After complete engagement of a parking braking system that contains a park lock device, the affected wheels must not move. The manufacturer must specify on which axle or axles the park lock device acts, “on the vehicle in a visible position in indelible form” or in another freely available way (para. 5.1.4.5.4.). The rule on disconnection of the parking braking system now also covers the park lock device and no longer includes the words “or by an ADS”.
Warning signals for the park lock device (paras 5.2.1.26.2.3., 5.2.1.26.6.)
New paragraph 5.2.1.26.6. covers a parking braking system that contains a park lock device and has detected at standstill a request to apply it. A red warning signal must then flash until the park lock device is completely engaged, “unless the parking braking system is preventing further movement of the braked wheels”. Where a separate red warning signal that meets all requirements of 5.2.1.29.3. normally indicates actuation of the park lock device, this signal must be used. In paragraph 5.2.1.26.2.3., the word “clamping” is replaced by “engagement” in the condition for suppressing the flashing red warning signal.
One braking control for each secondary braking test condition (Annex 4, para. 2.2.7.)
Under new paragraph 2.2.7. of Annex 4, only one braking control must be used for each secondary braking test condition of paragraph 2.2.5. Examples are the service braking control and the parking brake control. A different braking control may be used in the unladen and the fully laden condition, as described by the vehicle manufacturer in Annex 2.
Q2Why it changed
- Proposed by
- Experts from CITA (brake demand values); experts from CLEPA and OICA (park lock device); experts from OICA (secondary braking test); experts from CLCCR, CLEPA and OICA (e-axle trailers)
- Working party
- GRVA, 23rd session (September 2025)
Reasons
The Chair of GRVA presented the draft supplement and recommended its submission to AC.1. It includes provisions for the approval of trailers with e-axles (dynamo function), which aim to increase the efficiency of these vehicles. It also includes provisions on reference data for testing Electric Transmission Braking Systems during periodic technical inspections.
Sources (2)
“The Chair of GRVA presented the draft supplement to UN Regulation No. 13 (Heavy vehicle braking) including provisions for the approval of trailers with e-axles (dynamo function) aimed to increase the efficiency of these vehicles”
“also provisions on reference data for the testing of Electric Transmission Braking System during periodic technical inspections. He recommended its submission to AC.1.”
CITA proposed to enable the live reading of brake demand values during periodic technical inspections (PTI). CITA said that this is crucial for enhancing road safety, because it gives more accurate assessments of brake system performance. The aim was to include PTI provisions for electrical transmission braking systems in heavy duty vehicles. These provisions were to be non-discriminatory for Contracting Parties that apply the reference forces method. According to CITA, the requirement is only about reading the brake demand value, and it does not permit any modification or manipulation of that value. As a condition for adoption, GRVA supported that all new vehicle approvals and extensions to existing approvals would need to comply after 24 months.
Sources (4)
“aimed to enabling the live reading of brake demand values during Periodic Technical Inspections (PTI), which is crucial for enhancing road safety by ensuring more accurate assessments of brake system performance”
“aims to include pertinent provisions for Periodic Technical Inspection (PTI) regarding electrical transmission braking systems in Heavy Duty Vehicles (HDV) in a non-discriminatory way for Contracting Parties applying the reference forces method”
“pertains solely and exclusively to the reading of a specific value, as it is the brake demand value, and under no circumstances does it involve, imply, or permit the modification or manipulation of said value or any other”
“GRVA noted and supported as a condition for adoption the paragraph in the justification section stipulating that all new vehicle approvals and extensions to existing type approval would need to comply the requirements after 24 months”
CLEPA recalled that their proposal aimed at allowing for the type approval of park locks. The proposal addressed the type approval of a park lock device as an alternative to, or in combination with, the friction parking brake. ECE/TRANS/WP.29/GRVA/2025/13, on which the proposal is based, aimed to let a park lock device fulfil the static requirements for parking braking systems. That document said that the word “engagement” seems more appropriate than “clamping”, because the vehicle is kept in a static position. That document also said that the manufacturer gives additional information to enable periodic technical inspections of a park lock device.
Sources (5)
“The representative of CLEPA recalled the purpose of their proposal for amendments to UN Regulation No. 13 (ECE/TRANS/WP.29/GRVA/2025/34) aimed at allowing for the type-approval of park-locks”
“addressing the type-approval of a park lock device as an alternative to or in combination with the friction parking braking to hold the vehicle. It is based on ECE/TRANS/WP.29/GRVA/2025/13 amended by GRVA-20-06/Rev.1”
“This amendment aims to enable the use of a park lock device as an alternative to a friction type parking braking system to fulfil the static requirements of UN Regulation No. 13 for parking braking systems.”
“As the combination of friction type and park lock device or a combination of both will keep the vehicle in a static position, the word “engagement” seems more appropriate than “clamping””
“To enable periodic technical inspections for a Park Lock Device, additional information is provided by manufacturer.”
OICA proposed to clarify that any braking system control may be used to test the effectiveness of the secondary braking system in failure conditions. Different interpretations existed, and some Technical Services asked for the same braking system control in both laden and unladen test conditions. According to OICA, the content and the performance requirements do not change. Only the test duration and the effort to check complex vehicle designs are optimized.
Sources (3)
“The proposal aims to clarify that the use of any braking system control for testing the effectiveness of the secondary braking system in failure conditions is allowed.”
“The issue is that different interpretation exists, leading some Technical Services to request the usage of the same braking system control in both laden and unladen test conditions.”
“Neither the content nor the performance requirements are changing, but only the test duration and the efforts needed to check complex vehicle designs”
Proposer's reason (informal document GRVA-23-11-Rev.2)
Until a further amendment is agreed, trailers with electric propulsion and electric regenerative braking systems are to stay outside the scope of this Regulation. The power of the dynamo function is limited to protect motor vehicle functions of heavy vehicles, such as mass estimation, from relevant impact. A target electric power of 20 kW covers most use cases, for example the supply of cooling systems for O3 and O4 trailers. Paragraph 5.2.2.26.2. aims to avoid locking of wheels that the dynamo function affects. Below a braking rate of 0.04, like the friction value of wet ice, wheels will not lock. During tests, retardation forces of the dynamo function are not to support the performance of the braking functions.
Submitted by the experts from CLCCR, CLEPA and OICA. Working party adoption: ECE/TRANS/WP.29/GRVA/23, para. 63.
Sources (5)
“Until further amendment of Reg 13 is developed and agreed, trailers with electric propulsion and electric regenerative braking systems shall not be in the scope of Reg 13 approvals.”
“power of the dynamo function shall be limited to protect motor vehicle functions of heavy vehicles like mass estimation from relevant impact by the trailer dynamo function”
“An electric power of 20 kW is a target value which covers most use cases of a dynamo function e.g. supply of cooling systems for O3 and O4 trailers.”
“purpose of this requirement is to avoid locking of wheel(s) that are impacted by the dynamo function. If the wheels braking rate is below 0.04 (like the friction value of wet ice), wheels will not lock.”
“During testing the performance of the braking functions shall not be supported by retardation forces of the dynamo function.”
Document trail
- 2024-11ProposalECE/TRANS/WP.29/GRVA/2025/13Proposal by experts from OICA and CLEPA on the park lock device
- 2025-04ProposalECE/TRANS/WP.29/GRVA/2025/34Proposal by experts from CLEPA and OICA on park lock device approval
- 2025-07ProposalECE/TRANS/WP.29/GRVA/2025/43Proposal by experts from CITA on reading brake demand values
- 2025-09RevisedECE/TRANS/WP.29/GRVA/2025/46/Rev.1Revised proposal by experts from OICA on the secondary braking test
- —Amended in sessionGRVA-23-07-Rev.2Changes by CLEPA and OICA to the park lock proposal
- —Amended in sessionGRVA-23-18-Rev.1Changes by CITA, OICA and CLEPA to the CITA proposal
- —RevisedGRVA-23-11-Rev.2Proposal by experts from CLCCR, CLEPA and OICA on e-axle trailers, replacing ECE/TRANS/WP.29/GRVA/2025/15
- —Working party adoptsECE/TRANS/WP.29/GRVA/23GRVA session report, paras. 57, 59, 61 and 63
- 2025-12Sent to WP.29ECE/TRANS/WP.29/2026/6Text that GRVA sent to WP.29 and AC.1
- 2026-03WP.29 adoptsECE/TRANS/WP.29/1190Adopted at the 198th session (session report, para. 114)
- 2026-09-30In forceC.N.398.2026.TREATIES-XI.B.16.13UN depositary notification
Q3Who is affected
Vehicle manufacturer
- Keep the retardation power of the dynamo function at or below 22 kW for the complete O3 or O4 trailer.
- Add the 22 kW statement for multiple trailer combinations of Category O3 and/or O4 to the owner’s manual.
- If the dynamo function can generate a braking rate above 0.04 per wheel, control it so that it “does not cause wheel locking and has no critical impact on the vehicle behaviour”.
- Prepare evidence that O3 and O4 trailers comply with Annexes 13 and 21 with the dynamo function enabled.
- Describe how to display and access the brake demand value(s) (para. 5.1.4.6.2.1.).
- Specify on which axle or axles the park lock device acts (para. 5.1.4.5.4.).
- For parking braking systems with a park lock device, check that the affected wheels do not move after complete engagement.
- Check how disconnection of the parking braking system is controlled, because the rule no longer includes “or by an ADS”.
Component supplier
- Where a suitable electronic vehicle interface exists, check that the brake demand value(s) can be read through it.
- Give the vehicle manufacturer the data to describe how to display and access the brake demand values.
- Give the vehicle manufacturer the data for the Annex 18 assessment of the dynamo function (para. 5.2.2.26.3.).
- Make sure that your park lock devices consist of components of an adequate strength.
Technical service / Approval authority
- Check the maximum power of the dynamo function at type approval with one of the four methods of paragraph 5.2.2.26.1.
- For a dynamo function under paragraph 5.2.2.26.2., check the comparison tests with and without it active (para. 5.2.2.26.5.).
- If surface friction is too high or braking rate too low to lock the wheels, agree with the manufacturer “a way to increase the retardation power or reduce the vertical axle load of the e-axle”.
- Check that the e-axle functions and any dynamo function are not used in Annex 4 brake applications.
- In secondary braking tests, check that only one braking control is used for each test condition (Annex 4, para. 2.2.7.).
- Accept a different braking control for the unladen and fully laden conditions if the manufacturer describes it in Annex 2.
- Check the red warning signal of parking braking systems with a park lock device against paragraph 5.2.1.26.6.
- Complete the new item 14.18. on e-axles with a dynamo function in the Annex 2 communication.
- Note the 24-month period in paragraph 12.9.8. for the amendments to paragraph 5.1.4.6.2.1.
See every change side by side
RegVault customers compare every version of UN regulations, read the consolidated text and download the PDF.
ⓘ 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 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 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