R129 booster seats and booster cushions: the non-integral rules

How boosters are secured

i-Size booster seats and universal booster cushions are held by the adult three-point belt; ISOFIX attachments are optional and must be stowable §6.1.3.1. Specific vehicle versions may add maker-designed attachments, but only ISOFIX attachments may be used with an ISOFIX anchorage system §6.1.3.2. All non-integral seats are forward-facing only (Table 2).

If a booster has ISOFIX, it is dynamically tested with and without the ISOFIX attachments in use §6.6.4.1.7.

Stature limits

Belt guidance

A booster exists to put the adult belt on the strong parts of the child’s body. R129 requires that:

• there is one adult-belt route and a main load-bearing contact point at least 150 mm from the Cr axis §6.1.3.4;
• the lap belt is positively guided on both sides so loads go through the pelvis, from the moment the child is seated; it passes over the top of the thighs, and the angles between the belt and the horizontal are greater than 10° §6.2.1.5;
• the shoulder belt is guided so the child’s torso and neck cannot escape §6.2.1.5;
• during the dynamic test, the lap belt must not pass fully beyond the dummy’s pelvis before maximum head excursion, assessed on high-speed video §6.2.1.9;
• belt routes are marked in green on the product — and only approved routes may be shown §4.6.2, §4.6.4.

The booster cushion sitting-height test

Because a cushion has no backrest, R129 makes sure it lifts the child high enough: with the cushion on a simulated test bench, the top of the child’s head must be at or above a plane 770 mm above the Cr axis §6.1.3.6. A measuring device (Annex 25) reads the sitting height, which is converted to the minimum stature the cushion may be declared for:

Intermediate values are interpolated and always rounded up — a measured 70.1 cm gives 136.05 cm, so the cushion cannot be declared below 137 cm. The declared lower stature must be equal to or greater than this value.

A separate restraint test checks that a cushion is not pulled out from under the child: a lower-torso body block is belted onto it and a 250 ± 5 N pull is applied; the cushion must stay under the block and inside the belt §7.1.3.7.

Head excursion for boosters

For forward-facing non-integral seats the dummy’s head may not pass planes BA and DA: 500 mm and 800 mm generally, 840 mm for DA with Q3/Q6, and 550 mm / 840 mm with the Q10 dummy (rebound not considered for DA) §6.6.4.4.1.1. No lateral test with Q10 is needed for i-Size booster seats whose upper limit is between 125 and 135 cm (Table 8, note 5).

Packaging and labels

Booster cushions carry a label (min. 60 × 40 mm) showing the lower stature limit X §4.8.5; a booster seat whose backrest can be removed carries a label on the backrest identifying the product and size range §4.11. The packaging notice for i-Size booster seats and universal booster cushions is set out in §14.2.2–14.2.3.