This study was funded by Skyltfonden, the Swedish Road Transport Administration. All views, conclusions and methods presented here are the authors and do not necessarily present the views of the Swedish Road Transport Administration 

Small infants are not a prominent group in traffic injury data. However, on a daily basis neonatal nurses struggle to help parents fit their small infants, ready to be discharged from the hospital, in infant car seats that are not suited for them. The fit of the harness is critical for protection in a crash situation and current regulations in UN R129 are not sufficient to ensure a good harness fit for very small infants. In addition, prematurely born infants are especially sensitive to sitting posture, where unsuitable postures may cause heart and breathing problems during normal car travel. In many parts of the world, the care of premature infants is moving towards earlier discharge from hospital and regular check-ups, which means that many of these infants will increase their car travel exposure. 

Today, there is a lack of tools that can be used by car seat manufacturers to assess the fit of infant car seats. Our previous project (TRV2023-103118) resulted in three body shape models of premature infants based on anthropometric measurements for the 5th, 50th, and 95th percentiles in supine position. Only the 5th percentile body shape model was imported to a CAD software and enhanced with joints for the shoulders, elbows, hips and knees. This enabled repositioning of the model into a sitting posture, to assess the fit of infant car seat designs with CAD. The 5th percentile CAD-model was evaluated at CYBEX, identifying several needs for improvement. Therefore, the purpose of this project was to further develop tools that represent the prematurely born infants’ body shapes, that can be used by car seat manufacturers to assess harness and seat fit early in the production process. 

This project was composed of three work packages: 

1.     Improve the user-friendliness of repositioning the 5th percentile CAD-model, add a neck joint, and subsequently create 50th and 95th percentile CAD models using the same methodology.

2.     Add a landmark for the head centre of gravity (CG) in the small infant body shape models, such that sitting postures with unstable head positions can be identified in the CAD models. This included a search of the literature to find background references for the head CG location. 

3.     Disseminate the improved versions of the body shape and CAD models of the 5th, 50th, and 95th percentile premature infants, by uploading to the PIPER platform (http://www.piper-project.org/downloads). This included documentation of the morphing scripts and the baseline model, used for morphing to the different anthropometries.

All three work packages were successfully finished. The main project result was three CAD-models of small infants that can be used to evaluate and improve the fit and protection of infant car seats. The head and limbs of these models can be rotated into different sitting postures, where the head CG and CG for the whole body can be used in the assessment of seat design. 

With these improved tools, car seat manufacturers can improve the infant car seats, which contributes to increased road traffic safety, such that the prematurely born or extremely small infants’ first car journeys can be safe and secure.