Usability and Vehicle/Child Restraint Compatibility

As implementations of LATCH hardware in vehicles and on child restraints have evolved over the past decade, problems with incompatibilities between vehicles and child restraints remain. Caregivers also make mistakes when securing their children in the child restraint harness. Several different rating systems have been proposed to improve the usability of child restraints, reduce misuse, and increase compatibility between the child restraint and vehicle. Except for some label and instruction issues, usability is not an explicit part of FMVSS 213.

NHTSA developed an Ease-of-Use (EOU) Rating system (NHTSA 2006) to provide consumers with information about which child restraints have features that enhance usability. The system has provided strong incentives for child restraint manufacturers to improve products, labeling, and instruction manuals with respect to usability. The rating system includes questions that address each child restraint area related to the most common misuse modes. NHTSA has also proposed a voluntary vehicle/child restraint fit evaluation program to encourage vehicle manufacturers to provide information to consumers about compatibility for vehicle/child restraint pairings (NHTSA 2011). Vehicle manufacturers would submit lists of child restraints that are compatible with a particular vehicle based on a number of key installation factors.

In the field, some misuse modes arise from features and elements of the vehicle environment and others result from interactions between specific child restraint and vehicle combinations. A usability rating scheme has been issued by the ISO Child Restraints Group that has rating forms for all three elements: the child restraint, the vehicle, and specific combinations of the two (ISO 2010, Pedder and Hillebrandt 2007). This rating system currently focuses on ISOFIX (LATCH-type) systems. Some of the vehicle features that are rated in the current version of the ISO document include the vehicle owner’s manual instructions on how to identify the number and location of seating positions available for child restraint installation, the visibility and labeling of the LATCH anchors, the presence of other hardware elements that could be mistaken for LATCH anchors, the actions required for preparing the seating position for child restraint installation, and conflicts between LATCH and seatbelts.

The SAE Children’s Restraint Systems Standards Committee has drafted a new recommended practice to improve compatibility between child restraints and vehicles during LATCH installations (SAE 2009). The document defines tools and procedures for evaluating hardware in vehicles and on child restraints to improve their ease-of-use. Factors include measuring the force required to attach LATCH strap connectors to lower anchorages, measuring the clearance around lower anchorages, and recommendations for maximum size of LATCH connector hardware. Since the recommended practice is still in draft form, vehicle and child restraint manufacturers are likely not using the proposed methods regularly.