Rear seat safety for children aged 4-12: identifying the real-world needs towards development of countermeasures

This study summarizes a joint research project aiming to further enhance the safety of booster-seated children (aged 4-12) in the rear seat of passenger cars. The focus is real-world aspects of child safety, comprising the whole context of the vehicle and child restraints, and a variety of crash situations, including pre-crash events. Real children sit in a variety of sitting postures in cars. On-road driving studies show that children take different postures due to comfort, visibility or activities. The results from three studies 18 children in a variety of restraints, showed that for only a portion of the time, they are sitting upright with contact to the seatback, i.e. similar to the standardized crash test dummy position. When using a booster with protruding head side supports the children sit forward leaning more than without, and in a large share of the time, the head is in front of the head side supports. Approximately 40% of the crashes are preceded by evasive maneuvers. When exposing child volunteers to evasive braking they will move forward by up to 0.2m, when shoulder belt remains over the shoulder. Thirty four child volunteers were exposed to evasive braking and steering events, using different types of boosters. Depending of the size of the child and the booster used, they might slide out of the shoulder belt in steering events. In addition, existing child crash test dummies were tested and compared to the volunteer data. The volunteer data was also used to validate an active child Human Body Model, as a first step to develop a tool that can be used for evasive maneuvers. The booster is essential for the child enabling good interaction to the seatbelt. In addition, the vehicle protection systems play an important role for the child protection. Hence, for enhancing real-world safety it is essential to replicate in-vehicle situations. Unfortunately, this is not how child restraints are certified today. This study shows that child crash test dummies benefit from side airbags and advanced seatbelt technologies, and are responsive to changes in sitting postures and crash modes. In addition to the in-crash protective systems evaluated in this study, pioneering maneuver and run-off-road tests with crash test dummies were run to evaluate the effect of an electrical reversible seatbelt retractor (pre-pretensioner) to help keep the occupant in the belt during such an event. International multidisciplinary workshops were held and concluded that future advancements need to be data driven and incorporate multiple disciplines. Engineering advancements should strive towards less complex solutions and the shared responsibility between the child restraint and the vehicle was highlighted. The results from this project contribute to identification and quantification of important real-world needs, as well as evaluation and development of countermeasures. It is concluded, that from a real-world perspective, the vehicle and child restraint should be designed together targeting a range of acceptable common user positions; sitting postures preferably guided by comfort and positive means. Such designs will ensure robust function of the protection systems for these young occupants, and advance the development of countermeasures that protect children in real- world crashes, also including dynamic events prior to a crash.