## 1 Introduction  
In 2018, around 1038 children died in motor vehicle traffic crashes in the USA. It was also estimated that 190,000 children were injured. Of the 1038 children in motor vehicle accidents, 797 were occupants, and the rest were non-occupants (pedestrians, cyclists, and others). Child safety seats have been shown to reduce fatal injury by 71% for infants under one year old and 54% for toddlers (1 to 4 years old) in passenger cars [1]. The child restraint system (CRS) aims to protect the infant according to weight and age in case of a car accident. In addition, the manufacturers include instructions for the correct use of the CRS [2]. However, from a statistic where 285 infants used a CRS, 22.2% implemented it poorly. The most recurrent error was an inadequate selection of the CRS class, followed by inadequate positioning of the CRS infant and incorrect orientation [3]. The American Pediatric Association recommends the use of low-back boosters (LBBs) for children aged 4-8 years or weighing 18-36 kg [4], and the International Organization for Standards (ISO) 13216 describes a universal system for anchoring a CRS named ISOFIX. This standard specifies the general dimension requirements for rigid anchors for CRS in vehicles. A rigid anchor system holds the child seat directly to the vehicle's body [5]. Statistical data from frontal crashes showed that the most frequent injury in infants was to the head. However, since a small child has a large head mass and a fragile neck structure, the neck loading may cause a severe or fatal injury [6]. The neck usually experiences the inertial load generated by the head; during the initial phase of the shock, more restriction is applied to the lower neck, while the head is usually subject to a horizontal translation displacement of the torso, which induces neck extension movements. The neck is exposed to significant mechanical loads when the natural range of extension and flexion of the neck is reached, causing elongation and even tearing in different ligaments, leading them to an extreme point of the anterior dislocation of the joints [7]. There are designs of coupling systems for CRS that provide additional protection to the infant, dissipating the child's kinetic energy and the CRS during the crash. One of them is the vehicle seat interlock system, which consists of an interlock mechanism between a seatback latching mechanism and a child seat latching mechanism. The interlock mechanism allows the child seat to be deployed when the seat back is in its typical upright and latched condition [8]. In 1977, a system was designed consisting of compressible shock absorber assemblies and friction coupling portions, which absorbed some of the kinetic energy of the vehicle impact through the sliding movement of the CRS about the support bars and the vehicle seat, which was named an apparatus with a child seat and an energy absorption mechanism [9]. In 1980, a modified CRS called child's safety seat for vehicles consisted of a seat mounted on a frame adapted to the structure to allow for rotational movement and maintain the center of gravity of the seat with the infant below the means of pivoting [10]. In 2015, a new design called \"Crash indication system for a reclining ride down child seat\" consisted of a base to support the lower part of the CRS, which allowed the CRS to move on itself depending on the magnitude of the external force applied. A ratchet connection prevented the carriage from returning to its resting position [11]. Some variants of designs or systems for mounting a CRS provide additional protection for infants. However, those systems only fulfill their function under frontal impact conditions. A coupling device for a CRS allows displacement and the dissipation control of kinetic energy during the vehicular impact in a traffic accident. This research aims to evaluate the behavior and performance of a CRS mechanical coupling with ISOFIX during a lateral and frontal impact.