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.

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.

11. GRSP agreed to defer discussion on ECE/TRANS/WP.29/GRSP/2021/20 on the updating of drawings of fixtures for booster seats, to its December 2022 session, awaiting more evidence of crash situations with real vehicles, of side impact and offset configurations.