Abstract
The aim of this paper is to present both, the possibilities and the limits of the ISOFIX system. Although ISOFIX shows no better test measurement values than ideal installed conventional restraint systems, its benefits have been identified in the reduction of misuse. The effect of a third connection of ISOFIX was investigated and the aspect of a general market introduction is discussed.
The high usage rate of Child Restraint Systems (CRS) has significantly improved the safety of children in cars. But the anchorage of conventional CRS with the adult seat belt often causes problems leading to major misuse. New GDV studies revealed that even today serious misuse still occurs in about 30% of the CRS in practical use. The increased safety requirements for the anchorage of CRS are difficult to combine with continued optimisation of the adult seat belt. ISOFIX solves these problems and offers a defined, permanently correct anchorage of the CRS, with easier handling and misuse reduction.
This report relates to test results comparing conventional CRS (CCRS) and ISOFIX systems using the ECE test bench and real car seats. Within the ideal test configuration, ISOFIX systems show no further benefit compared to CRS, but the latter are more frequently exposed to misuse in practice which may lead to dummy loads that are higher by 30-40%. The different tests on car seats showed that ISOFIX measurement values are clearly below the legal limits (only head excursion is close to the limit) and that the values are significantly better than the comparative values using the ECE test bench. General market introduction and user acceptance urgently require a universal type approval of ISOFIX and thus an amendment of ECE-R 44. In so doing, the requirement must be that every ISOFIX system fulfil the present legal regulations by using the two lower
ISOFIX anchorages only which are already internationally harmonised.
This study also analysed the effect of an additional top tether; three forward facing ISOFIX seats were subjected with/without a top tether to the FMVSS 213 procedure using a BMW 3 car body with the real seat bench. The top tether values (even head excursion) showed no major improvement and some problems regarding increased chest acceleration. The neck torques generally exceeded the reference limit of 20 Nm. A final international decision regarding a third support should be taken soon, but should be based on comprehensive concrete test results. The different support requirements for forward and rearward facing systems have to be considered as well as proven effectiveness, influence regarding misuse, and biomechanical loads especially to the neck. ISOFIX is not only a modification of a conventional CRS with improved anchorages. It is the opportunity to develop a totally new concept with new solutions for manufacturers and users. By developing the legal framework for ISOFIX and with universal approval, it should be carefully observed that the technical innovative potential of ISOFIX systems will not be restricted but rather promoted, especially in view of daily practical use.