UN R13 Supplement 6 (13 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 6 to the 13 series of amendments
Supplement 5 → 6
- What changed
- The parking braking system may now use a park lock device for the static parking brake requirements, with new rules in paragraphs 5.1.4.5.3. and 5.2.1.26.6.
- New paragraph 5.2.2.26. sets dynamo function rules for e-axle trailers, including a 22 kW retardation power limit for a complete O3 and/or O4 trailer.
- The conditions for disconnection of the braking surfaces or the park lock device of the parking braking system no longer include “or by an ADS”.
- Why
- The park lock proposal aimed to allow the type approval of park lock devices.
- The provisions for the approval of trailers with e-axles (dynamo function) aimed to increase the efficiency of these vehicles.
- The OICA proposal aimed to clarify that any braking system control may be used to test the secondary braking system in failure conditions.
Q1What changed52 changes
Park lock device in the parking braking system (para. 5.2.1.10.)
The parking braking system may now use a park lock device to meet the static requirements of Annex 4, paragraphs 2.3.1 and 2.3.2. The park lock device may replace the means acting on the braking surfaces or work in combination with them. The park lock device must consist of components of adequate strength and be as effective as layouts that act only on the braking surfaces. After complete engagement of a parking braking system with a park lock device, the affected wheels must not move. The conditions for disconnection of the braking surfaces now also apply to the park lock device, as relevant, and no longer include “or by an ADS”. The text also changes the reference from paragraph 5.2.1.7.2.1. to paragraph 5.2.7.1.2.1. above, “one second” to “1s” and “remote control device” to “remote-control device”.
Park lock device: axle information and warning signals (paras. 5.1.4.5.3., 5.2.1.26.2.3. and 5.2.1.26.6.)
New paragraph 5.1.4.5.3. requires the manufacturer to specify on which axle or axles a fitted park lock device acts. The information must be visible and indelible on the vehicle, or freely available in another way, for example a handbook or electronic data record. New paragraph 5.2.1.26.6. covers a parking braking system with a park lock device that has detected, at standstill, a request to apply it. Then a red warning signal must flash until the park lock device is completely engaged, unless the system prevents further movement of the braked wheels. If a separate red warning signal that meets paragraph 5.2.1.29.3. normally shows actuation of the park lock device, it must give this warning. In paragraph 5.2.1.26.2.3., the condition for suppressing the flashing red warning signal is now correct “engagement” of the parking brake, not “clamping”.
E-axle trailers: scope and definitions (paras. 1.2.6. and 2.45. to 2.47.)
Under new paragraph 1.2.6., this Regulation does not cover e-axle trailers with e-axles that provide electric propulsion and/or include an electric regenerative braking system. An “e-axle” is an axle mounted to a vehicle of category O that generates electrical energy and/or provides electrical propulsion. 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. Paragraph 2.47. defines the “dynamo function” of an e-axle trailer. It is the capability of a trailer to convert vehicle kinetic energy into electrical energy without affecting the forces developed by the braking system. A dynamo function is not part of the braking system and is not considered as a brake.
Requirements for the dynamo function of e-axle trailers (para. 5.2.2.26.)
Until uniform technical provisions have been agreed, trailers of Category O1 and O2 with a dynamo function must not be approved under this Regulation. The dynamo function must not provide over 22 kW of retardation power for the complete trailer of Category O3 and/or O4, checked at type approval. A dynamo function able to exceed a braking rate of 0.04 per wheel must not cause wheel locking or a critical impact on vehicle behaviour. The operation of the dynamo function must be assessed according to Annex 18. Trailers of Categories O3 or O4 must be shown to still comply with Annexes 13 and 21 when the dynamo function is enabled. For a dynamo function under paragraph 5.2.2.26.2., tests with and without it active must show no wheel locking and no critical impact on vehicle behaviour.
E-axles and the anti-lock system (Annex 5, paras. 2.2.1.2. and 2.2.1.3.)
In the case of an electrical failure of the anti-lock system, an e-axle function must now also be switched off automatically. Paragraph 2.2.1.3. now also requires anti-lock control of an e-axle, so that the axles it brakes cannot be locked by it above 15 km/h. Both paragraphs exclude an e-axle with a dynamo function if the prevention from locking the wheel(s) is not based on the anti-lock braking system.
E-axles and the dynamo function in Annexes 2, 4, 10, 19, 20 and 21
In Annex 4, paragraph 1.4.1.2.2. now says that the e-axle functions of an e-axle trailer must not be used during the brake applications. In Annex 4, new paragraph 1.7.1.3. says that a dynamo function, if any, must not be used during the brake applications. Annex 10, paragraph 1.1.1., now also excludes the retarding force of a dynamo function when determining the vehicle performance under that annex. In the tests of Annex 19, paragraphs 4.5.1.5. and 4.5.1.6., any dynamo function must also be disengaged. E-axles are added to Annex 19, Appendices 5 and 7 (schematic diagrams), Annex 20, paragraph 3.2.1.3., and Annex 21, paragraph 1.2.7. Annex 2 has a new item 14.18. on whether the trailer has an e-axle with a dynamo function.
Braking control in secondary braking tests (Annex 4, para. 2.2.7.)
New paragraph 2.2.7. of Annex 4 requires only one braking control for each test condition of the secondary braking effectiveness under paragraph 2.2.5. Examples are the service braking control and the parking brake control. This does not prevent a different braking control in the unladen and fully laden condition, as the vehicle manufacturer describes in Annex 2.
Q2Why it changed
- Proposed by
- Experts from CLEPA and OICA (park lock device), experts from CLCCR, CLEPA and OICA (e-axle trailers) and experts from OICA (secondary braking control)
- Working party
- GRVA, 23rd session (September 2025)
Reasons
The proposal from CLEPA and OICA addressed the type approval of a park lock device to hold the vehicle. The proposal covered a park lock device used as an alternative to the friction parking brake, or in combination with it. It is based on ECE/TRANS/WP.29/GRVA/2025/13 amended by GRVA-20-06/Rev.1 and ECE/TRANS/WP.29/GRVA/2025/14 amended by GRVA-20-07/Rev.1. ECE/TRANS/WP.29/GRVA/2025/13 aimed to let a park lock device meet the static requirements of UN Regulation No. 13 for parking braking systems. At GRVA, the representative of CLEPA recalled that the purpose of their proposal (ECE/TRANS/WP.29/GRVA/2025/34) was to allow the type approval of park locks. Several delegations noted that the revised proposal (GRVA-23-07/Rev.2) addressed the concerns that they had expressed at the previous session.
Sources (4)
“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”
“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.”
“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”
“presented a revised proposal (see GRVA-23-07/Rev.2). Several delegations noted that this proposal addressed their concerns expressed at previous session.”
The earlier proposal (ECE/TRANS/WP.29/GRVA/2025/13) said that the word “engagement” seems more appropriate than “clamping”. The reason given was that “the combination of friction type and park lock device or a combination of both will keep the vehicle in a static position”. It also said that the manufacturer provides additional information, to enable periodic technical inspections of a park lock device. At GRVA, CLEPA clarified that the test for periodic technical inspection was not part of their proposal and would be addressed at European level.
Sources (3)
“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.”
“CLEPA clarified that the test for PTI was not part of that proposal and that it would be addressed at European level.”
The OICA proposal aimed to clarify that any braking system control may be used to test the secondary braking system in failure conditions. Different interpretations existed, and some Technical Services requested the same braking system control in both laden and unladen test conditions. The proposal said that neither the content nor the performance requirements change. It said that only the test duration and the efforts 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”
At WP.29, the Chair of GRVA presented the draft supplement to UN Regulation No. 13 with provisions for approving trailers with e-axles (dynamo function). These provisions aimed to increase the efficiency of these vehicles. At GRVA, CLEPA presented a revised proposal (GRVA-23-41) that focused on the approval of the dynamo function for e-trailers.
Sources (2)
“including provisions for the approval of trailers with e-axles (dynamo function) aimed to increase the efficiency of these vehicles”
“presented (GRVA-23-41) a revised proposal focusing on the approval the dynamo function for e-trailers”
Proposer's reason (informal document GRVA-23-11-Rev.2)
The proposers said that trailers with electric propulsion and electric regenerative braking systems stay out of scope until a further amendment is agreed. They said that the power limit protects functions of heavy motor vehicles, like mass estimation, from relevant impact by the trailer dynamo function. They gave 20 kW of electric power as a target value that covers most use cases, for example cooling systems for O3 and O4 trailers. With conversion losses taken into account, they said that a maximum retardation power of 22 kW has a tolerable impact on motor vehicle functions. They said that wheels with a braking rate below 0.04, like the friction value of wet ice, will not lock. They said that, if the braking rate is higher, a control function must avoid wheel locking.
Submitted by 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.”
“a retardation power of maximum 22 kW will impact the motor vehicle functions, which is tolerable”
“If the wheels braking rate is below 0.04 (like the friction value of wet ice), wheels will not lock. If the braking rate is higher, a control function shall avoid locking of wheels.”
Document trail
- 2024-11ProposalECE/TRANS/WP.29/GRVA/2025/13Park lock proposal for UN Regulation No. 13 by experts from OICA and CLEPA
- 2024-11ProposalECE/TRANS/WP.29/GRVA/2025/15Proposal for e-trailers by experts from CLCCR, CLEPA and OICA
- 2025-04RevisedECE/TRANS/WP.29/GRVA/2025/34Park lock proposal for UN Regulations Nos. 13 and 13-H by experts from CLEPA and OICA
- 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.2Revised park lock proposal by experts from CLEPA and OICA
- —RevisedGRVA-23-11-Rev.2Revised e-axle trailer proposal by experts from CLCCR, CLEPA and OICA
- —Working party adoptsECE/TRANS/WP.29/GRVA/23GRVA session report, paras. 59, 61 and 63
- 2025-12Sent to WP.29ECE/TRANS/WP.29/2026/12Text 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.400.2026.TREATIES-XI.B.16.13UN depositary notification
Q3Who is affected
Vehicle manufacturer
- If you use a park lock device, make sure it is as effective as layouts acting only on braking surfaces.
- Make sure the affected wheels do not move after complete engagement of a parking brake with a park lock device.
- For vehicles with a park lock device, specify on which axle or axles it acts (paragraph 5.1.4.5.3.).
- Mark the park lock axle information on the vehicle visibly and indelibly, or make it freely available in another way.
- Make sure the red warning signal for a park lock device meets the new paragraph 5.2.1.26.6.
- If an ADS controls the disconnection of the parking braking system, check this design against the new disconnection conditions.
- Make sure the dynamo function gives no more than 22 kW retardation power for a complete O3 and/or O4 trailer.
- State in the owner’s manual that 22 kW limits all dynamo functions together in a multiple O3/O4 trailer combination.
- If the dynamo function can exceed a braking rate of 0.04 per wheel, control it to prevent wheel locking.
- Be ready to show that O3 or O4 trailers still meet Annexes 13 and 21 with the dynamo function enabled.
- For a trailer with a dynamo function under paragraph 5.2.2.26.2., be ready for comparison tests with and without it active.
- If you use different braking controls for unladen and fully laden secondary braking tests, describe them in Annex 2.
Component supplier
- If you supply park lock devices, make sure they consist of components of adequate strength.
- If your parking braking system has a park lock device, make sure its red warning signal meets paragraph 5.2.1.26.6.
- For vehicles under Annex 5 (ADR), check how your e-axle meets the new anti-lock rules of paragraphs 2.2.1.2. and 2.2.1.3.
- Be ready to show e-axles in the schematic diagrams of system configurations under Annex 19.
Technical service / Approval authority
- When you assess a park lock device, check that it is as effective as layouts acting only on braking surfaces.
- Check that the manufacturer specifies on which axle or axles the park lock device acts (paragraph 5.1.4.5.3.).
- Check the red warning signal for a park lock device against paragraph 5.2.1.26.6.
- When you assess disconnection of the parking braking system, use the new conditions without “or by an ADS”.
- At type approval, check the maximum dynamo power with one of the methods in paragraph 5.2.2.26.1.
- Assess the operation of the dynamo function according to Annex 18 (paragraph 5.2.2.26.3.).
- Check that e-axle functions of an e-axle trailer are not used during the brake applications, as Annex 4 now requires.
- Check that a dynamo function is not used during the brake applications of Annex 4, paragraph 1.7.1.3.
- Check that the Annex 2 item 14.18. shows whether the trailer has an e-axle with a dynamo function.
- Accept a different braking control for unladen and fully laden secondary braking tests, as the manufacturer describes in Annex 2.
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ⓘ This report gives advice only. It is not legal or type-approval advice.
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