Overview
ISO 13216-4:2020 specifies requirements for lower tether anchorages (LTA) used to attach lower tethers for rearward-facing child restraint systems (CRS) in road vehicles. The standard defines positioning zones, dimensional and installation requirements, general and static strength requirements, and requirements for retrofit LTAs. It is intended to improve usability, reduce misuse and vehicle interior damage, and increase safety by standardizing pre‑installed lower tether anchorages for rearward-facing CRSs.
Key Topics
- Scope and applicability
- Applies to all vehicle seating positions intended by the manufacturer for rearward-facing CRSs (outer and mid rear seats, third row, and front passenger seat).
- Covers both factory-installed LTAs and mounting points for retrofit installations.
- Positioning and reference method
- Positioning zones are defined relative to the ISO/R2 envelope (installed with seat adjusted to its rearmost position); Annex A provides a procedure for non‑ISOFIX positions.
- If two LTAs are used per CRS position, minimum separation is 280 mm; they must not be on the same side of the envelope centreline and the offset between centrelines shall not exceed 200 mm.
- If a single LTA is used it must be symmetrically positioned within ±50 mm of the envelope centreline.
- Rearmost surface of the zone is positioned 100 mm rear of a vertical plane through the ISO/R2 reference point.
- Dimensions and design
- Anchorages must provide openings/clearance (square, circular or semi‑circular) compatible with standard top tether connectors per ISO 13216-2.
- LTAs should be shaped to minimize injury risk (no sharp edges/protrusions).
- LTA placement must avoid common support‑leg zones and allow practical routing without damaging interior components.
- Strength and testing
- Strength testing considers a CRS plus child total mass up to 40 kg.
- If the LTA is attached to vehicle parts already approved under relevant regulations (examples include UN R14, FMVSS 207, etc.), additional strength requirements may be deemed satisfied.
- Annex B details requirements and testing for retrofit LTAs.
- Instructions and marking
- Clause 6 sets requirements for user instructions and marking to support correct use.
Applications
- Vehicle manufacturers: design and integrate LTAs into new vehicles and prepare mounting points for retrofit kits.
- CRS manufacturers: design tether connectors and test compatibility with LTA zones and dimensions.
- Test laboratories and regulators: perform LTA strength testing and conformity checks.
- Aftermarket installers and OEM service teams: install retrofit LTAs to the Annex B criteria.
Related Standards
- ISO 13216-1 (ISOFIX seat bight anchorages)
- ISO 13216-2 (Top tether anchorages and attachments)
- ISO 13216-3 (CRS classification and vehicle space)
- Referenced vehicle structural/regulatory frameworks (e.g., UN regulations, FMVSS) for existing type‑approval strength criteria
Keywords: ISO 13216-4:2020, lower tether anchorages, LTA, child restraint systems, CRS, ISOFIX, retrofit anchorages, tether strength testing, vehicle safety.