UN R129 Supplement 1 (05 series) · UNECE Regulation No. 129 (ECE R129) — Uniform provisions concerning the approval of Enhanced Child Restraint Systems used on board of motor vehicles (ECRS).
UN R129 — Supplement 1 to the 05 series of amendments
Base text → Supplement 1
- What changed
- Paragraph 6.6.4.3.1.: head acceleration during dummy contact with a rigid part of the test bench in the rebound phase is not considered.
- For this paragraph only, the 100 mm diameter bar of paragraph 6.6.4.4.1.2.1. is not a rigid part of the test bench in the rebound phase.
- Paragraph 6.6.4.4.1.1. loses its two subparagraphs (d), which had the rebound-phase contact rule.
- Why
- The Regulation was inconsistent on whether rebound head movement and contact count for the head acceleration requirement.
- The change gives consistency between child restraint systems and between laboratories with different test bench designs.
Q1What changed3 changes
Dummy contact with a rigid test bench part in the rebound phase (para. 6.6.4.3.1.)
Paragraph 6.6.4.3.1. gives the injury assessment criteria for frontal and rear impact. A new paragraph there covers dummy contact with a rigid part of the test bench in the rebound phase. The head acceleration criterion during that contact is not considered. For this paragraph only, the 100 mm diameter bar of paragraph 6.6.4.4.1.2.1. is not a rigid part of the test bench in the rebound phase.
Two subparagraphs (d) deleted (para. 6.6.4.4.1.1.)
In paragraph 6.6.4.4.1.1., the first and the last groups of subparagraphs each had a subparagraph (d). It said that the head acceleration criterion is not considered during dummy contact with a rigid part of the test bench in the rebound phase. The amendment deletes both subparagraphs (d).
Q2Why it changed
- Proposed by
- Expert from CLEPA
- Working party
- GRSP, 79th session (June 2026)
Reasons
The proposal removes rebound head contact from the head acceleration requirement for all child restraint systems.
Sources (2)
“This proposal removes rebound head contact from the head acceleration requirement for all CRSs.”
“to remove rebound head contact from the head acceleration requirement in UN Regulation No. 129 for all Child Restraint Systems (CRS)”
Contact was explicitly excluded for forward-facing integral CRS and Q10 booster cushions; nothing was stated for booster seats or Q6 booster cushions.
Sources (3)
“UN Regulation No. 129 is inconsistent as to whether rebound head movement and contact is taken into account for the head resultant acceleration requirement.”
“For example, dummy contact is explicitly excluded for forward-facing integral CRSs and also for booster cushions when tested with the Q10 dummy.”
“However, nothing is stated for booster seats or for booster cushions tested with the Q6 dummy.”
Test bench designs vary, so a booster seat can pass the type-approval test in one laboratory but fail in another due to rebound head contact.
Source
“Variations in test bench design mean that a booster seat can pass the type-approval test in one laboratory, but fail in another due solely to rebound head contact.”
The change gives consistency between CRS in the Regulation and between laboratories with different test bench designs.
Source
“It ensures consistency between CRSs within UN Regulation No. 129 as well as consistency and reproducibility between laboratories that feature different test bench designs.”
It also harmonizes with UN Regulations Nos. 94 and 137, which calculate resultant head acceleration excluding rebound movement of the head.
Source
“It also harmonizes with the approach taken for adult dummies in UN Regulation Nos. 94 and 137”
Document trail
- 2026-03ProposalECE/TRANS/WP.29/GRSP/2026/2CLEPA proposal on rebound head contact
- —Working party adoptsECE/TRANS/WP.29/GRSP/79Session report, para. 24
- 2026-09Sent to WP.29ECE/TRANS/WP.29/2026/198Text that GRSP sent to WP.29 and AC.1
- PendingWP.29 voteScheduled for the 200th session (17–20 November 2026)
- PendingIn forceDate not yet known
Q3Who is affected
Vehicle manufacturer
- Review head acceleration results that include dummy contact with a rigid part of the test bench in the rebound phase.
- Note that the 100 mm bar of paragraph 6.6.4.4.1.2.1. is not a rigid part of the test bench here.
Component supplier
- No direct action for this role.
Technical service / Approval authority
- Ignore head acceleration during dummy contact with a rigid test bench part in the rebound phase.
- For this rule only, do not treat the 100 mm bar of paragraph 6.6.4.4.1.2.1. as a rigid test bench part.
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ⓘ This report gives advice only. It is not legal or type-approval advice.
More UN R129 change reports
- 05 series — Base text
- 04 series — Supplement 6
- 04 series — Supplement 5
- 04 series — Supplement 4
- 04 series — Supplement 3
- 04 series — Supplement 2
- 04 series — Supplement 1
- 04 series — Base text
- 03 series — Supplement 12
- 03 series — Supplement 11
- 03 series — Supplement 10
- 03 series — Supplement 9
- 03 series — Supplement 8
- 03 series — Supplement 7
- 03 series — Supplement 6
- 03 series — Supplement 5