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UN R139 Supplement 3 (00 series) · UNECE Regulation No. 139 (ECE R139) — Uniform provisions concerning the approval of passenger cars with regard to Brake Assist Systems.

UN R139 — Supplement 3 to the 00 series of amendments

Supplement 2 → 3

Adopted at the WP.29 199th sessionEntry into force not yet known
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What changed
  • New paragraph 1.2.3. adds vehicles of Categories X and Y to the vehicles that this Regulation does not cover.
  • New paragraph 5.7. says that, while an ADS feature is active, the BAS must not influence the performance of the braking system.
  • Footnotes 1 and 3 now cite document ECE/TRANS/WP.29/78/Rev.8 of the Consolidated Resolution on the Construction of Vehicles (R.E.3.).
Why
  • The Brake Assist System (BAS) is a driver assistance feature and therefore has no role while an ADS is performing the DDT.
  • If an ADS causes the movement of a brake pedal, the amendment will make sure that such movement does not influence the brake performance.

Q1What changed4 changes

Vehicles of Categories X and Y not covered (para. 1.2.3.)

New paragraph 1.2.3. adds “Vehicles of Categories X and Y” to the vehicles that this Regulation does not cover under paragraph 1.2.

Vehicles of Categories X and Y.

BAS while an ADS feature is active (para. 5.7.)

New paragraph 5.7. says that, while an ADS feature is active, the BAS must not influence the performance of the braking system.

Whilst an ADS feature is active, the BAS shall not influence the performance of the braking system.

Footnotes 1 and 3 cite document ECE/TRANS/WP.29/78/Rev.8

Footnote 1 now begins “As defined in the Consolidated Resolution on the Construction of Vehicles (R.E.3.)” and cites document ECE/TRANS/WP.29/78/Rev.8. Before, it began “M1 and N1 categories of vehicles are defined in” and cited document ECE/TRANS/WP.29/78/Rev.4, para. 2. Footnote 3 on the distinguishing numbers of the Contracting Parties to the 1958 Agreement now cites document ECE/TRANS/WP.29/78/Rev.8 in place of ECE/TRANS/WP.29/78/Rev. 4. Both footnotes now give the web address https://unece.org/transport/vehicle-regulations/wp29/resolutions.

M1 and N1 categories of vehicles are As defined in the Consolidated Resolution on the Construction of Vehicles (R.E.3.), document ECE/TRANS/WP.29/78/Rev.4, para. 2 -www.unece.org/trans/main/wp29/wp29wgs/wp29gen/wp29resolutions.htmlECE/TRANS/WP.29/78/Rev.8, https://unece.org/transport/vehicle-regulations/wp29/resolutions
The distinguishing numbers of the Contracting Parties to the 1958 Agreement are reproduced in Annex 3 to the Consolidated Resolution on the Construction of Vehicles (R.E.3), .), document ECE/TRANS/WP.29/78/Rev. 4, Annex 3 - www.unece.org/trans/main/wp29/wp29wgs/wp29gen/wp29resolutions.htmlECE/TRANS/WP.29/78/Rev.8 - https://unece.org/transport/vehicle-regulations/wp29/resolutions
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Q2Why it changed

Proposed by
Task force on regulatory fitness for Automated Driving Systems
Working party
GRVA, 24th session (January 2026)

Reasons

  • The Brake Assist System (BAS) is a driver assistance feature and therefore has no role while an ADS is performing the DDT. For this reason, the proposal says that this Regulation is not applicable for vehicles of Categories X and Y. The proposal describes these as vehicles with a manual driving capability only below 6 km/h.

    Sources (2)
    “Brake Assist System (BAS) is a driver assistance feature and therefore has no role whilst an ADS is performing the DDT.”
    “For this reason, this regulation is not applicable for vehicles of Categories X and Y (i.e. with a manual driving capability only below 6 km/h).”

  • The proposal adds a new provision to make sure that the BAS is not influencing the braking system performance whenever an ADS feature is active. This is while the ADS is performing the DDT.

    Source
    “It is also proposed to add a new provision to ensure the BAS is not influencing the braking system performance whenever an ADS feature is active (i.e. whilst the ADS is performing the DDT).”

  • Both categories of BAS defined in this Regulation rely on driver input for their activation, so such a change may not be necessary. However, if an ADS causes the movement of a brake pedal, the amendment will make sure that such movement does not influence the brake performance.

    Sources (2)
    “Recognizing that both categories of BAS defined in this regulation rely on driver input for their activation, such a change may not be necessary”
    “however if an ADS causes the movement of a brake pedal, this amendment will ensure that such movement does not influence the brake performance.”

Document trail

  1. 2025-11ProposalECE/TRANS/WP.29/GRVA/2026/6Task force proposal for several UN Regulations, including No. 139
  2. —Working party adoptsECE/TRANS/WP.29/GRVA/24Session report, para. 35 (a)
  3. 2026-04Sent to WP.29ECE/TRANS/WP.29/2026/83Text that GRVA sent to WP.29 and AC.1
  4. 2026-06-24WP.29 adoptsECE/TRANS/WP.29/1192Adopted at the 199th session (session report, para. 103)
  5. PendingIn forceDate not yet known

Q3Who is affected

Vehicle manufacturer

  • Check whether your vehicle types are of Categories X and Y. This Regulation does not cover them.
  • Make sure that the BAS does not influence the performance of the braking system while an ADS feature is active.

Component supplier

  • Make sure that your BAS does not influence the performance of the braking system while an ADS feature is active.

Technical service / Approval authority

  • Check that the BAS does not influence the performance of the braking system while an ADS feature is active.

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ⓘ This report gives advice only. It is not legal or type-approval advice.

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