10. GRSP resumed discussion on ECE/TRANS/WP.29/GRSP/2021/20, tabled by the expert from Spain, which provides updates of drawings of fixtures ISO/B2 and B3 (for assessing the external dimensions of an Enhanced Child Restraint System (ECRS)) for booster seats volumes to allow the possibility of a support leg. The expert from CLEPA provided more evidence from impact tests and simulations to justify the proposal (GRSP-72-36 and item 10, para. 28).

11. GRSP adopted ECE/TRANS/WP.29/GRSP/2021/20, amended by annex III to the session report. The secretariat was requested to submit the proposal as draft Supplement 4 to the 08 series of UN Regulation No. 16 (Safety-belts) for consideration and vote at the June 2023 sessions of WP.29 and AC.1.

12. GRSP resumed discussion on ECE/TRANS/WP.29/GRSP/2021/25 (UN Regulation No.16), tabled by the expert from CLEPA to improve the compatibility between the support leg volume and the fixtures to assess the volume of an ECRS. GRSP noted the justifications for this proposal in GRSP-72-36.

13. GRSP adopted ECE/TRANS/WP.29/GRSP/2021/25, not amended. The secretariat was requested to submit the proposal as part of (see paragraph 11 above) draft Supplement 4 to the 08 series of UN Regulation No. 16 (Safety-belts) for consideration and vote at the June 2023 sessions of WP.29 and AC.1.

28. Referring to the decision taken under agenda item 5 (see paragraphs 10 to 13 above), GRSP considered GRSP-72-36 and resumed discussion on ECE/TRANS/WP.29/GRSP/2021/26 as a parallel proposal to the UN Regulation submitted by the expert from CLEPA. Finally, GRSP adopted ECE/TRANS/WP.29/GRSP/2021/26 as amended by annex V to the session report. The secretariat was requested to submit the proposal as part of (see paragraph 27 above) draft Supplement 9 to the 03 series of UN Regulation No. 129 (ECRS) for consideration and vote at the June 2023 sessions of WP.29 and AC.1.

9. The expert from Spain introduced GRSP ECE/TRANS/WP.29/GRSP/2021/20 in a presentation (GRSP-70-03), updating drawings of fixtures of booster seats to allow the seats to be designed in combination with a support leg as anti-rotational systems. The proposal caused concern with GRSP experts for the effects on UN Regulation No. 145 (ISOFIX anchorage systems, ISOFIX top tether anchorages and i-Size) and real-world crashes. GRSP agreed to resume discussion on a revised version of ECE/TRANS/WP.29/GRSP/2021/20 (UN Regulation No. 16), at its May 2022 session with more evidence of the crash situation in real vehicles, in side impact and offset configuration.