ISO 29061-5:2026 — Child Restraint Systems — Booster System Installation and Child Securing

Introduction

ISO 29061-5:2026, developed by ISO/TC 22/SC 36, specifies criteria for judging the usability of booster seat child restraint systems (CRSs) when installing them and securing a child. Booster systems are belt-positioning devices where the vehicle seat belt serves as the primary restraint for the child. This second edition replaces ISO 29061-5:2017. The standard covers backless booster cushions, booster seats with seatbacks, integrated booster systems, and combination products.

Booster systems bridge the gap between harnessed CRSs and adult seat belts. Proper belt positioning across the child’s shoulder and pelvis is critical for crash protection.

Evaluation Forms and Scoring

The evaluation is performed in three steps: separate assessment of the booster system, usability assessment when installing in specified vehicle seating positions, and securing a child in the booster system. Two evaluation forms are used.

Form	Focus	Key Assessment Parameters
Form 1	Booster system separate evaluation	Labels, instructions, design features, ISOFIX/top tether provisions
Form 2	Interface and child securing	Installation ease, belt routing, child positioning, removal

The same good/average/poor (3/1/0) multiplied by importance A/B/C (3/2/1) scoring system applies. The procedure takes approximately 30 minutes. Equipment includes the evaluation form, vehicle owner’s manual, CRS instruction manual, and a force gauge for belt tension measurement.

Engineering Design Insights

Critical Design Features for Booster Usability

The evaluation examines: belt routing guides (clarity of path for lap and shoulder belts), vehicle belt buckle accessibility, ISOFIX attachment provisions (rigid or flexible), top tether provisions, support leg operation, shoulder belt positioning device effectiveness, and overall stability of the booster on the vehicle seat. Hidden slack—unintended strap looseness that is not easily detectable—receives particular attention.

Practical Implications for Design and Selection

Manufacturers should provide clear visual indicators for correct belt routing and booster positioning. Self-explanatory labels that can be understood through pictures alone significantly improve usability scores. The standard applies the ISOFIX term to include flexible attachments such as LATCH (USA) and UAS (Canada), acknowledging global variations in CRS attachment systems. Vehicle-integrated booster systems can also be evaluated using this procedure.

Booster systems are distinct from harnessed CRSs. The vehicle seat belt is the primary restraint, so correct belt fit across the child’s skeletal structure (shoulder and pelvis) is essential. Poor belt positioning can cause submarining or abdominal injury in a crash.

FAQs

Q1: What types of booster systems are covered?
A: Backless booster cushions, booster seats with seatbacks, integrated booster systems, and combination convertible products.

Q2: How is ISOFIX defined for booster systems?
A: As in Part 1, ISOFIX includes both rigid attachments (per ISO 13216-1) and flexible attachments such as LATCH (USA) and UAS (Canada).

Q3: What is a vehicle seat belt positioning device?
A: A device that maintains the appropriate shoulder strap position on the child’s torso, ensuring correct belt fit across the collarbone and chest.

Q4: Does the evaluation include vehicle integrated boosters?
A: Yes, the procedure can also be used for evaluation of vehicle integrated booster systems.