PASSIVE SAFETY IMPROVEMENTS IN CHILD RESTRAINT SYSTEMS PLACED IN REAR SEATS OF VEHICLES BY INTRODUCING A NEW ISOFIX ACCESSORY

摘要

In a 3-abreast seating configuration whenever there is a child restraint system (CRS) present, and especially if it is an ISOFIX one, occupants of the central position miss the room needed in order to rest their back properly against the backrest making them prone to suffer serious whiplash injuries in frontal or rear crashes or to collide with the adjacent passengers in lateral crashes. This lack of space jeopardizes the safety of all occupants as the restraint systems cannot work properly if the passengers are not correctly seated; more so, it affects further the safety of children making safety belt fastening difficult and uncomfortable and causing their CRS to be removed prematurely from the car to give room for that third occupant. Most of those problems can be tackled by introducing an accessory to be inserted between the vehicle ISOFIX anchorages and the CRS ISOFIX connectors, which allows to move laterally the CRS, while keeping that ISOFIX connection, from the CRS nominal position to an extreme position where the CRS is shifted aside resting against the door panel, or at least coming quite close to it. Due to limited resources, full capacity tests have not been possible running 3-abreast configurations. To assess technical feasibility and performance, the device was submitted to the tests specified in the ECE R129 standard, comparing sled tests carried out with the CRS alone (baseline reference case) with those same CRS coupled with the device shifting their nominal position 70 mm towards the door panel to establish potential safety improvements. CRS selection was based on their popularity within the Spanish market, and the tests were performed using both Q6 and Q10 dummies for each combination. The analysis of the results of the dynamic tests carried out showed improvements in the level of side impact protection. For instance, the average HPC15 (Head Performance Criterion), directly related with the expected level of damage in the event of an impact, measured for the Q6 dummy was 232.76, while the average HPC15 with the same seats moved closer towards the door panel was 225.08, a 3.3% improvement in average with improvements for one of the CRS of up to 22.5%. For the Q10 dummy, the results were similar with an average HPC15 of 103.75 for the stand-alone CRS and an average HPC15 of 99.23 for the CRS coupled with the accessory device, a 4.4% improvement in this case. In every test performed, the resulting values remained below the limits designated in ECE R129 for the injury assessment criteria. The introduction of this new device could lead to important benefits on the safety of families, and children in particular, by providing an effective use of the central seat by any passenger or additional CRS, while retaining the ISOFIX connection for a CRS placed in a lateral seat. Specifically, side protection could be significantly improved preventing undesired yaw rotations, and the optimized space usage will allow extending the CRS usage period avoiding their premature removal due to the lack of space.