This part of ISO 13216 classifies the spatial requirements in a vehicle to enable a child restraint system (CRS) to be conveniently mounted. It also specifies the dimensions of child restraint systems, in order to ensure that they will fit in vehicles. A classification scheme is provided to determine dimensional compatibility between child restraint systems and the available space at specified seating positions in vehicles. The dimensional requirements refer to forward-facing child restraint systems of three size categories, rearward-facing child restraint systems of three size categories, and lateral-facing child restraint systems of two categories.