In February 2007, the Consumers Union, through Consumer Reports magazine, published its own crash test data showing that many child safety seats “failed disastrously” in collisions that more closely simulate “real-world” accidents than the crash tests mandated by the National Highway Transportation Safety Administration (NHTSA)[2].
The child safety seats were tested in the same manner as new cars in the federal New Car Assessment Program (NCAP), which is the government program that assigns ratings to new cars based upon how safely they perform in crash tests. Currently, the NCAP tests vehicles in 35 mph frontal crashes and 38 mph side impacts. The only government mandated child safety seat test is a 30 mph frontal crash. The results of the Consumer Reports testing showed that models which had previously been recommended now failed the new, more stringent tests. Moreover, the test results showed that increased cost does not equate to a safer child safety seat, as the two seats that passed all of the more stringent testing cost less than $100.
History
The first dedicated child restraint on the world market was the Kangol, sold in Britain in 1963. Since 1975 Australia has mandated that Type-A restraints (those equivalent with rear facing infant seats) be designed to distribute forces in frontal crashes, as well as side impacts, rollovers, and accidents where the vehicle was rear-ended[3] . In 1978, Tennessee became the first state to enact laws requiring the use of child safety seats for children up to age four. In 1981, Federal Motor Vehicle Safety Standard (FMVSS) 213 came into effect requiring dynamic testing of child safety seats. The federal requirement was changed in 1985 to require that all child safety seats pass FMVSS 213 without use of a tether, which is an attachable top strap used to limit motion of the child safety seat. This change came about due to widespread non-use of the tethers, which had been utilized by some models in order to meet the previous requirements of FMVSS 213. In addition, by 1985, all 50 states had enacted laws requiring the use of child safety seats.
In March of 1999, FMVSS 225 was enacted to standardize installation of child safety seats independent of the vehicle seat belts and required that most passenger cars come equipped with user-ready tether anchorage points. It also mandated a phase-in of rigid anchorage bars in the bight (seat crack) so that the child safety seats may snap into them. This system is called LATCH.
Rear-Facing Infant Seats
Rear-facing infant seats should be designed to distribute the deceleration forces across the back of the infant during an accident sequence. An infant’s neck is not typically strong enough to restrain his or her head given the deceleration forces encountered in a collision so it is preferable for forces to be spread across the back of the infant by the seat back. In order for this to occur, it is necessary that the proper back angle be maintained. Maintaining the proper child safety seat back angle prevents the infant from ramping up the seat and striking his or her head on an object beyond the seat edge, or possibly ramping fully out of the seat. Proper seat positioning is often indicated by a level or a ball-and-rocker device on the seat bottom. Many owners’ manuals accompanying child safety seats will advise parents to place a rolled-up towel beneath the rear edge of the child safety seat so as to accomplish the desired seat back angle. The issue then becomes maintaining that seat back angle and limiting downward deflection once forces are applied to the seat in a collision.
Many factors contribute to downward deflection of the seat back in an automobile collision. The length of the seat bottom, for example, can change the amount the seat back is allowed to rotate. If the seat bottom is significantly shorter than the base of the child safety seat, (allowing the child safety seat to hang over the edge of the seat-bottom) there will, in effect, be a longer “lever arm” such that the seat is then able to rotate further downward [4]. In Australia, it is mandatory that a tether be attached from the top of the child safety seat to the rear shelf in the passenger automobile. This tether limits the degree to which the child safety seat can rotate forward and down. In Britain, some designs of child safety seats include a support that extends from the base of the child seat to the vehicle floorboard. This “foot” is designed to maintain proper seat back positioning and prevent downward deflection.
Once the appropriate seat back position angle is achieved, the next consideration is the harness that holds the infant in the seat. Infants, especially newborns, do not have prominent shoulders due to the need to pass through the birth canal. Accordingly, the need for proper restraint of the hips is a critical, though often poorly warned about feature of child safety seats.
Most parents installing a child safety seat for the first time pay special attention to the positioning of the shoulder straps, as they should, because that is often the portion of the owners manual accompanied with red lettering and highlights drawing attention to the critical need for the shoulder straps to be properly positioned. In contrast, some owners manuals treat the proper positioning of the hip and crotch strap as an afterthought, instructing the parent to do nothing more than position where comfortable for the infant. Given the narrowness of the infant’s shoulders, it is necessary that the belts going across the top of the femur be secure so that the infant’s legs are not able to rotate under the hip restraints and then slide free [5]. This is achieved by proper positioning of the crotch strap and adjusting the length of those straps going across the femurs, if that feature is available.
The positioning and width of the shoulder straps should not be ignored either. The shoulder straps should be positioned in accordance with the manufacturer’s recommendations, which is, generally near the top of the shoulders, but not above them. An important tool in maintaining the width of the shoulder straps is the chest clip. The chest clip should be positioned so it is centered on the chest at the armpit level. This will help to hold the straps onto the shoulders before a crash. When evaluating chest clip designs, consideration should be given to whether the chest clip has an anti-slip backing. This is available on some chest clips and is helpful in keeping the chest clip at the proper location. Another consideration is the width of the chest clip. Some designs currently have the clip, which holds the two straps, positioned in the middle, between those straps. Other designs actually have the fastener holding the straps together on top of the straps, which allows to two straps to be positioned more closely.
Another concern with regard to the positioning of shoulder straps is aftermarket pads. Some manufacturers offer “comfort pads.” These pads typically consist of a horseshoe shaped pad which goes up and around the infants head and has a tail portion which goes down the seat back. If the tail portion of the comfort pad is cut too widely, or does not fit the within the slots for the shoulder straps, it can spread the shoulder straps increasing the risk of the infant slipping between the shoulder straps and beyond the edge of the child safety seat.
Forward Facing
It is recommended that the longer you can keep a child rear-facing, the better, as it allows the forces of the collision to be dispersed along the entire length of the torso and head. The American Academy of Pediatrics recommends children more than one year old and between 20-40 pounds be in a forward facing child safety seat with a five-point harness. One significant difference with regard to harness positioning in a forward facing seat as opposed to a rear facing seat is the recommendation that the shoulder straps be at or above shoulder level for toddlers in a forward facing seat [6].
An emerging issue is what to do with children who exceed the weight limits for the seat, but who do not fit a standard booster seat. The standard forward facing child seat is designed for children 1 to 4 years old who weigh up to 40 pounds. To accommodate children who weigh more than 40 pounds, but who are not tall enough to use a booster seat, Britax along with Cosco have introduced forward facing child seats that can accommodate 65-80 pounds.
Booster Seats–Forgotten Child
In 1986, the National Transportation Safety Board published a study describing the dangers associated with lap-only rear seat safety belts. This study found that the lack of upper torso restraint lead to abdominal, neck, and spinal cord injuries from instances where the body hyperflexed and rotated over the lap restraint resulting in injury.
In 1987, automakers faced with mounting regulatory pressure, announced that they would voluntarily install lap/shoulder belts for the outboard positions in the rear seats of vehicles. However, the design and testing for the lap/shoulder belts in the rear seat mimicked that for the front seat occupants and failed to focus on those passengers most likely to be seated there, specifically children and smaller adults. The only requirement with regard to lap/shoulder belt combination and children was that the lap portion of the belt be long enough to fit around a child. These designs resulted in lap/shoulder belts that could contact the child’s face, throat, and neck. This fit was both uncomfortable and potentially dangerous, as the shoulder strap could act as a fulcrum resulting in neck and spinal cord injuries. An industry response to the problem of poor fit was to recommend that the shoulder portion of the belt be placed behind the child, effectively placing them in a lap-only restraint. As a result, safety advocates began recommending booster seats to close the fit gap between Child Safety Seats and proper fit in a vehicle’s original safety belt system.
The concept of booster seats to properly position adult seat belt systems originated in Australia and Sweden at about the same time in 1978. A belt positioning booster seat is designed to raise the child up on the vehicle seat so that the lap/shoulder belts fit correctly. The Centers for Disease Control (CDC) recommends that children start using a booster seat when they outgrow their convertible child safety seats per the manufacturer’s size and weight limits for that respective seat. Children should remain in booster seats until such time as they are 58 inches tall, have a sitting height of 29 inches and weigh 80 pounds. The CDC goes on to recommend that all children 12 years of age and younger ride in the rear seat of a vehicle whenever possible, regardless of whether they require a booster seat.
As of July 1, 2006, 38 states and the District of Columbia had enacted laws requiring the use of booster seats or other appropriate restraint devices for children who have outgrown their forward-facing child safety seats, but who are still too small to fit an adult restraint system correctly. Notably, Florida is not one of the 38 states that have enacted provisions specifically requiring use of a booster seat to bridge this gap. For those states that have, booster seat laws vary widely, but all include an age limit, and many include height and weight limits.
Conclusion
The installation of a child safety seat is often a frustrating and difficult experience for parents. Child safety seats are the only mandated consumer product that require a 40 hour course to become a certified installer. It is imperative for the safety of the children that may be riding in them that careful consideration is given to the model purchased and proper fit and installation. This article has attempted to highlight some areas that are often overlooked, but vitally important.
Please note that the content of this article is a summary only, and should not be relied upon as a substitute for manufacturers’ safety information and instructions.
