Quantification of Infant Car Seat Vibration over a Mission Profile

Little is known about the effect of vibration associated with vehicle travel on the comfort and health of infants. Variations in vehicle speed associated with travelling under typical suburban driving conditions influence the vibrational response of the vehicle body, which affects the vibration transferred to an infant. The aim of this investigation is to quantify the vibration of an infant car seat over a mission profile. The translational and rotational acceleration of the car seat was measured during 15 repeated runs and weighted according to BS 6841(1987). The mission profile resulted in a range of different translational and rotational vibrations of the infant car seat for the various sections of the mission profile. Vertical acceleration was the largest of the accelerations encountered along the mission profile. The variations in the infant car seat vibrations were quantified by the relative difference. The sections of the mission profile have a median relative difference of 15.59%, with an interquartile range of 17.49% (\( IQR = 75^{\text{th}} \;{\text{percentile}} - 25^{\text{th}} \;{\text{percentile}} = 27.38\% - 9.89\% \)), with large relative differences (>80%) observed for traffic lights. Approximately 58% of the sections of the mission profile indicated relative differences greater than the relative difference threshold of the 75^th percentile adult occupant. Therefore, these variations are most likely large enough for certain sections of the mission profile to subject participants to different stimuli and, in turn, result in different cardiorespiratory responses.