3-point harness

A harness found only on infant-only restraints consisting of shoulder straps coming together at a buckle in the shell or on a crotch strap; not to be confused with 3-point (lap-shoulder) belts. See also Harness types.

5-point harness

A CR harness that has a webbing strap over each shoulder, one on each side of the pelvis, and one between the legs, with all five coming together at a common buckle. See also Harness types.

5-Step Test - see also Belt-positioning booster

ALR - see Automatic locking retractor

Acceleration

A measure of how fast a body (mass) gains or loses velocity as the result of a force being applied to that body. Deceleration is negative acceleration.

Adjustable upper anchorage (AUA)

A system built into the vehicle that raises or lowers the shoulder belt anchorage to help place and keep the belt crossing the shoulder between the neck and arm. See also Shoulder belt positioner.

Aftermarket accessory

A product designed to be used in conjunction with child restraints or vehicle belts for improving comfort, fit, or installation or for providing solutions to issues of child behavior. Most of these are not covered by federal regulations, but some have been voluntarily tested by their manufacturers under conditions similar to FMVSS 213. If so, the manufacturer should be able to provide test results upon request. However, some test results may be misleading, because available crash dummies are not able to assess abdominal injury potential. (See also Belt-shortening clip, Belt tightener, Harness strap cover, Locking clip, Padded inserts, Shoulder belt positioner. More on this topic: Transport Canada, Third-Party Aftermarket Products for Children’s Restraint Systems.) (3/07)

Air bag

Front passenger air bags and rear-facing restraints do not mix. Air bags are stored in the instrument panel and need a certain amount of space in which to inflate before they begin to act as energy-absorbing cushions for larger occupants. A rear-facing restraint in the front seat places the child's head and body very close to the air bag housing, and direct impact from the air bag can be fatal to an infant. Older children who are leaning toward the dashboard, with or without a lap-shoulder belt, and unrestrained children who are thrown forward from pre-impact braking are also at risk of a broken neck if the air bag catches them under the chin. Children tightly restrained in a CR with a harness are probably the least likely to be injured by an air bag, but it is still a good idea to put them in the rear seat unless the air bag is disconnected. The same applies to car beds. If front-seat use is necessary, the vehicle seat should be in its farthest rearward position.

Side-impact air bags are much smaller and emerge with less force. There are no studies published thus far that indicate a child properly restrained in a CR is at risk from current side-impact air bags, but laboratory simulations indicate that unrestrained and out-of-position children could be injured, including those leaning against the door while sleeping. NHTSA recommends that children not be placed next to active side air bags unless the vehicle manufacturer states that it is safe. For best protection, the child should be restrained in an age- and size-appropriate CR or booster in the center rear position. If there are side-impact air bags in the rear seat and the child must be in an outboard seat, do not leave any objects, such as toys or even pillows, between the child or CR and the door. In addition, if the child is in a booster, remind her not to lean out of the booster and to keep head, arms, and legs away from the door. For more information, see Transport Canada, March 2006.

Anchor – A common short alternative for anchorage; often used to refer specifically to the hardware installed at the anchorage, as in a retrofit shoulder-belt or tether kit. See also Top tether.

Anchor point - A location identified in a vehicle where anchorage hardware, usually for a retrofitted top tether anchorage, may be installed.

Anchorage – A strong point and associated hardware in a vehicle to which a vehicle belt or LATCH attachment is secured. See Adjustable upper anchorage, Child restraint anchorage system, LATCH anchorage, Lower anchorage, Top tether anchorage.

Angle of recline, forward-facing

The most common recommended orientation for a forward-facing CR is the most upright position. Many convertibles and some child seats have two or more choices of seating angle for forward-facing use, and each of these positions must be certified to FMVSS 213. Although the most upright position probably still provides the most effective overall restraint in terms of load distribution to appropriate bony structures, a certified reclined position may be used for a sleeping child or to make the CR match the angle of the vehicle seat for a tighter installation. It is a good idea, however, to try the most upright position first, because the upright geometry of the CR coupled with the angle of the vehicle seat cushion may sufficiently recline the child to be comfortable.

For children seated directly on the vehicle seat, in a backless booster, or in a booster with adjustable back, the normal seatback angle is about 20° to 30° from vertical. This comfort-angle range also applies to adults. If the seatback is tipped farther back than this, there is a danger of the occupant sliding under the safety belt, called submarining, during a crash. This is not a problem in a forward-facing CR, because the entire shell is reclined, not just the seatback, which reduces the likelihood of submarining. Submarining in a CR is also limited by the crotch strap holding the lap straps down on the thighs.  

Potential injury from spinal loading, predicted in the early days of CR design, has not been shown to be a problem in actual crashes. One laboratory study in England found that a forward-facing CR had to be tipped more than 50° from vertical to generate harmful loading to the dummy, and this is more reclined than acceptable for forward- or rear-facing CR use. (9/07)

Angle of recline, rear-facing

The back surface of a rear-facing CR should be between 30° and 45° from vertical, starting with the most reclined angle for a newborn and becoming more upright as the baby grows. This recommendation is a balance between crash protection and comfort. If the CR is too upright, the head could flop forward uncomfortably and possibly pinch off the airway, especially for a newborn. If the CR is too reclined during a frontal crash, the infant could slide toward the top of the restraint, exposing the head to injury, especially for the larger, heavier baby.

Each manufacturer determines an optimum back angle for its products and specifies a way, such as a level indicator, for the user to determine that angle. However, these indicators only work when the vehicle is level, so they can sometimes be misleading. The Federal standard allows the back of a rear-facing CR to rotate downward as much as 70° from vertical during the FMVSS 213 crash test, but this extreme result reflects the test conditions and would not represent good crash performance. To meet these test requirements, some restraint manufacturers may install their position indicators so the initial angle is too upright for a small infant. For these situations, installing the seat with the indicator outside the specified zone may be necessary, or one must obtain a different safety seat. The baby’s airway must not be compromised.

To set an appropriate back angle for the child, install the CR in the car and put the baby in the CR with the buttocks in the deepest part of the CR and the baby's back straight. Jostle the CR a bit, and, if the baby's head flops forward (while awake or asleep), it is necessary to increase the angle. For infant-only restraints, some bases can be adjusted if more recline is needed, or a detachable base can be removed and the shell alone reclined a little more. Otherwise, for these and for convertibles, insert a tightly rolled towel or sheet or a foam "noodle" under the toe-end of the CR to compensate for the slope of the vehicle seat. Increase the angle of recline just enough to keep the baby's head from flopping forward, but no more than 45° from vertical.

The American Academy of Pediatrics currently recommends that infants born at less than 37 weeks gestation be monitored in a semi-upright position prior to discharge to detect possible breathing, oxygenation level, and/or heart rhythm problems (AAP, 2006). If a baby needs to be more reclined than 45°, he must be tested similarly in a car bed to see if discharge is appropriate, and if so the car bed must be used for travel. There is also evidence that prolonged (over an hour) semi-upright positioning may lead to reduced oxygen saturation levels even among term infants. It is therefore recommended that very young infants not be left undisturbed in their rear-facing child restraints for long periods.

As the child grows, becomes heavier, and can hold his head erect, the angle can be decreased, making the restraint more upright, to provide better crash protection. For a sleeping baby, this angle should be at least 30° from vertical. In addition to improved comfort, keeping the back of the baby's head in contact with the CR provides better protection in a crash. In some vehicles, the back seat may be too small to accommodate a convertible CR that is reclined as far as 45° in the rear-facing position. For older babies, the CR may be used at a more upright angle to make it fit in the car, but a newborn may require a smaller infant-only restraint. (9/07)

Automatic locking retractor (ALR)

A vehicle belt retractor that allows the belt to be pulled out initially but locks when the pull-out action stops and tension is again applied. The retractor keeps the belt from being pulled out farther until it is fully retracted again. These systems tend to tighten progressively while in use and can be found on older lap belts. See also Emergency-locking retractor, Switchable retractor.

BPB - see Belt-positioning booster

Back angle - see Angle of recline

Backless booster - see Belt-positioning booster

Backless child restraint

A type of booster, as defined by FMVSS 213, intended to distribute the loading of a lap belt over a wider area of the child’s body. It is required to be crash tested using only a lap belt and using the head excursion limit of 32 inches. Currently, no boosters of this type are sold in the U.S. Originally, all restraints of this type were shield boosters, which have a seating platform and a structure in front of the child for restraint. Shield boosters are no longer considered appropriate child restraints, because harnessed child restraints offer better protection for the sizes of children who can use shield boosters (under 40 lb). The Britax Laptop (now discontinued) did not have a boosting platform but had a similar-looking shield and was rated for children from 30 to 65 lb. The Laptop still considered a better choice than a lap belt only for children over 40 lb when shoulder belts are not available in the rear seat. (9/06)

Base - see Infant-only restraint

Belt-positioning booster (BPB)

A firm seating platform used with a lap-shoulder belt that raises the child relative to the safety belt system to improve lap-shoulder belt fit. Booster seats improve belt fit and crash protection in several ways. First, the booster seat raises the child so the height of the tops of the thighs and the shoulders are closer to those of an adult, for whom the belt system was designed. Second, raising the child changes the angle of the lap belt to be more vertical, which promotes loading of the lap belt on the pelvis rather than the abdomen. Third, the booster cushions are shallower than vehicle seat cushions, so a child’s knees can bend comfortably at the edge. This encourages a child to sit up straight with his back against the seatback, which also improves belt fit. Fourth, booster seats usually have guides or handles near the hips, which position the lap belt and lower part of the shoulder belt. These guides hold the lap belt low and flat across the child's upper thighs, while the same guide on the buckle side also pulls the shoulder belt toward the child, makes the belt angle more vertical, and helps position the shoulder belt across the center of the child's chest and between the neck and arm.

Never use a pillow or cushion as a booster seat for a child or an adult. In a crash, it can be compressed or slide out from under the occupant, resulting in a very loose belt. Other seats sold as chairs for children or to boost a child in an adult chair should not be used as booster seats in a vehicle, because they would not be able to route the belt correctly.

There are three types of BPBs: (A) backless boosters, (B) highback boosters (see also combination seats), and (C) removable-back boosters. Backless boosters can be used on any vehicle seat that supports the child's head to the top of the ears. These have the advantage of allowing the child to sit farther back in the seat, reducing head excursion, and to take advantage of the vehicle seatback's comfortable padding, contours, and back angle. Using a backless booster, which is not easily visible from outside the vehicle, may also be preferable for an older child who is reluctant to continue using a booster. Some backless boosters also have a shoulder belt guide on a strap attached to the base to allow adjustment of the shoulder belt position. Use of the shoulder belt guide is optional if the shoulder belt fits the child well without it.

Highback boosters are constructed with the base and seatback as a single unit and are often packaged as a combination seat. A removable-back booster consists of a base and seatback that can be used together, or the base can be used alone. A booster with a back is needed in vehicles with low seatbacks and no headrests to allow restraint of the child’s head in a rear impact. However, a few booster backrests must be supported by the vehicle seatback or headrest, so it is important to check the instructions carefully. Some highback and removable-back boosters have side impact protection features and/or lateral support features that can keep a sleeping child in position relative to the safety belt.

Both types B and C have shoulder belt guides or clips to help route the upper end of the shoulder belt. For designs with the clip, it is not necessary to route the shoulder belt through the clip if the shoulder belt fits well without it. Highback boosters are supposed to be limited in weight by FMVSS 213 to 4.4 kg (9.7 lb), to keep heavy boosters from loading the child from behind. However, NHTSA is not consistently enforcing this weight limit.

For any type of booster, the shoulder belt should be positioned about halfway between the neck and arm, not at the edge of the shoulder or rubbing on the neck. As long as the belt is snug, neck injury is not a prevalent problem, even if the belt touches the side of the neck, but it can be uncomfortable and may lead the child to put the belt under the arm or behind the back, which is very dangerous. Less mature or very active children may need some help staying correctly positioned for the entire trip. This might be encouraged by preventing the shoulder belt from loosening, either by locking the shoulder belt with its switchable retractor (if available) or by using a highback booster with a shoulder belt guide that does not allow the child to pull out the webbing. Be careful with some belt guides that may allow the child to lean forward and/or pull the belt out but have enough friction to keep it from automatically retracting again, as loose belts can result in injuries.

It is not recommended that a locking clip be used to keep an active child in position on a BPB or to keep an unstable BPB in place. In a collision, the child's upper body bends forward, loading the shoulder belt, which pulls the lap belt tight to prevent submarining. Using a locking clip to hold the two parts of the belt together could hold unwanted slack in the lap belt or prevent the lap belt from tightening as it should.

Because booster seats are positioning devices and not usually attached to the vehicle, they may shift around when children are entering or exiting the vehicle or sometimes during vehicle travel. Caregivers have asked, particularly with combination seats used as boosters, whether boosters can be attached to the vehicle with the top tether or lower attachments to prevent the shifting. Instructions for some boosters currently being sold allow them to be attached to the vehicle, so users should check their instructions to see if this is permitted.

Ideally, children should continue to use a CR with an internal harness until they have exceeded the height and/or weight limits. BPBs are the next step, but only for seating positions with lap-shoulder belts; they should not be used with lap belts alone. This is due to a number of factors. The head of a child sitting on a booster is higher and, with a highback booster, farther forward than the head of a child sitting directly on a vehicle seat. In addition, a lap belt going over both the child and the booster will be longer than a belt going over the child only. Without a shoulder belt to hold the upper torso back, the higher, more forward head position by itself increases the risk of head contact, but the added lap-belt length will allow even greater head excursion in a crash for a child on a booster than for a child on the vehicle seat.

Children should continue to use a BPB until both the lap-shoulder belt and vehicle seat cushion fit properly. The age at which a child “fits” the adult restraint will vary with the child and the vehicle. For example, short and heavy children tend to need boosters longer than tall and thin ones, but thin ones may not have sufficient pelvic girth for the lap belt to lie correctly. Since there are many combinations of child sizes, seat depths, and belt geometry, the only sure way to determine the need for a booster is to buckle the child into the belt and apply the 5-Step Test. (9/06)

Belt-shortening clip

Metal hardware used to fix the length of a lap belt with an emergency-locking retractor (ELR). It is sometimes called a "heavy-duty" locking clip. It should be used with either a lap-only belt having an ELR or with an ELR lap belt sewn separately to the lap-shoulder-belt latchplate. These types of belts are generally found only in pre-1996 vehicles. The CR is installed with the lap belt, then the excess belt webbing is pulled out, and the belt-shortening clip is used to lock a loop of webbing, so that the remaining length permits a tight installation of the CR.

It is important not to use a regular locking clip, supplied with the CR, when a belt-shortening clip is needed. They have the same shape, but the belt-shortening clip is usually thicker or made of stronger material. Some vehicle owner's manuals instruct parents on the use of a locking clip to shorten a belt without providing the information they need to distinguish between a regular locking clip and a belt-shortening clip. A belt-shortening clip can be used to do the job of a regular locking clip, but not vice versa.

Some of the clips have codes (numbers and letters) stamped into the metal, but these codes do not correspond with the part number on the package. Some of the clips have no identifying information stamped on them at all, and one (no longer made) had the misleading stamp “heavy duty.” The only way to identify a belt-shortening clip positively is to obtain the clip in the original packaging. Instructions must be followed carefully. If the packaging does not include instructions for belt-shortening, check the vehicle owner's manual. Use the part number below to order the clip from the dealer parts department. (9/07)
    Ford - F03Z-5461248-A
    Toyota - 73119-22010
    Nissan - H8010-89970

Belt stretch

Belt and harness webbing is a woven material that has a certain amount of "give." Belts were originally made of nylon, which would stretch about 13% under severe loading by a heavy adult occupant. Newer polyester webbing, used now in virtually all vehicle belts, stretches only about 7% at most. Most child restraint harness webbing is still made of nylon, because it has a softer texture than polyester, but the weight of a child is not enough to make it stretch much, if at all. Lap-belt stretch is also not a big issue for installed child restraints. If belt stretching does occur with a heavy adult, it can reduce the force of the belt on the chest by absorbing crash energy, but the trade-off is increased head excursion and possibly contact with the vehicle interior. Webbing stretch does not enhance ride-down, except to the extent it provides a small amount of energy absorption. Now that rear seats of stiffer larger vehicles, such as vans and SUVs, are being equipped with lap-shoulder belts, there is interest in again using webbing with controlled elongation to limit the force on the chest and thus minimize rib fracture and other internal injuries. Front seats, however, are likely to have mechanical load-limiters (see Vehicle belt enhancements) instead.

Belt tightener

An aftermarket device to wind up excess webbing and lock it in place. These products are not regulated by FMVSS 213, although manufacturers have advertised testing their products using similar procedures. When used to take up slack that could not otherwise have been eliminated by the installer, they may provide a valuable function. Current product designs and instructions, however, may require that more webbing be wound around the device than would be needed to augment normal tightening.

Bight - see Seat bight

Blanket - see Padded inserts, blankets, and bulky clothing

Booster - see Backless child restraint, Belt-positioning booster, Combination seat, Shield booster

Built-in child restraint system

A CR that is an integral part of a vehicle seat. These are tested according to FMVSS 213 with similar requirements as add-on CRs. The primary difference is the crash test "pulse," which may be more or less severe than the standard pulse, depending on the particular vehicle in which the CR will be included. Built-in restraints have the potential advantage of linking the child more directly to the vehicle (see Ride-down) and eliminating installation errors, but the disadvantage is that they cannot be moved. Some vehicle seats with built-ins are also found to be uncomfortable when used by adults. Current built-ins take the form of child seats, combination seats, and belt-positioning boosters. There are no built-in rear-facing restraints in production in the U.S. (9/06)

Button on lap-shoulder belt webbing

A button is often attached to lap-shoulder belt webbing to keep the latchplate from falling down out of reach. If this button prevents the belt from retracting far enough to secure the CR firmly, the button may be clipped off, taking care not to cut the belt.

CR - see Child Restraint System

Car bed

An infant restraint that allows the baby to lie flat, with the primary restraint surface being the side of the bed. This type of restraint should only be used by infants who can be discharged but may have medical problems that are aggravated by sitting semi-upright in a regular rear-facing infant restraint. The American Academy of Pediatrics recommends that infants born at less than 37 weeks gestation be monitored in a semi-upright position prior to discharge to detect possible breathing, oxygenation level, and/or heart rhythm problems (see AAP, 2006). This is called angle tolerance testing. The test should last one hour or the length of the ride home, whichever is longer. If the infant does not pass the test, she should be retested in a car bed to determine if discharge is appropriate. If so, the infant can be restrained for travel in a car bed, which is sometimes available for loan or purchase through the hospital.

In a car bed, the infant lies flat, preferably on his back, with a harness or bunting to hold the infant in position. The car bed is placed across the vehicle seat in the center position, or with the baby’s head toward the center of the vehicle (not towards the door) in an outboard seating position. During a frontal crash, the front side of the car bed distributes forces over the side of the infant’s body, with the harness providing restraint during rebound or rollover. For side impact, the infant would theoretically be safer in a standard rear-facing CR, especially if there is significant intrusion on the side of the vehicle closest to the infant’s head. There are not enough car beds used to document statistically the effectiveness of this type of restraint, although field experience has not demonstrated any widespread problems.

There are three car bed models available in the U.S., which accommodate infants from very low birth weight to an average 1-year-old. It is recommended that car beds be installed in the rear seat with an adult sitting next to it to monitor the infant, since the rear seat is less dangerous for all children and there is a potential for excessive loading by the air bag in the front seat. (9/07)

Carry handle

A semi-circular loop of hard plastic that is attached to each side of an infant-only restraint and can be rotated to various positions. It is used to carry the CR outside of the vehicle. Carry handles are only for carrying and do not lock the shell into the base. One product, no longer manufactured, used a carry handle made of fabric.>

During vehicle travel, the handle must be locked into one of the designated positions, which may be described as follows: 'up' is in the carrying position, 'back' is behind the head, and 'down' is the lowest position, pointed toward the floor. A fourth position, braced against the seatback, is not common here but is used in Europe and Australia to restrict rebound. Most manufacturers recommend locking the carry handle in the ‘back’ or ‘down’ position, although some allow and may even require the handles to remain 'up' during travel. Many handles are now being tested for use in the ‘up’ position and as anti-rebound devices. It is therefore necessary to read and follow the handle instructions for the specific CR used.

There have been some rare cases of injury from head contact with the handle. In these cases, the handle broke, and a child in a loose harness moved close enough to contact the damaged handle. In another case, a side curtain air bag broke the upright handle and allowed it to contact the child, causing minor injuries. Other injuries have occurred when the parents used the CR as a carrier outside the car, the handle rotated, and the baby slipped out of a loose or unused harness and fell to the ground. Several manufacturers of infant restraints have had recalls by the U.S. Consumer Product Safety Commission for handle breakage problems, so handle locking designs are now more reliable. However, parents should avoid swinging infants in a CR by the handle and always make sure the harness is secured and snug. (9/07)

Child restraint anchorage system

A standardized system of user-ready hardware in vehicles, consisting of two lower anchorages and one upper anchorage specified in FMVSS 225, for installing child restraint systems independent of the vehicle seat belt; popularly referred to as LATCH in the U.S. and similar to the Canadian Lower Universal Anchorage System (LUAS).

Child restraint fixture (CRF)

A physical model representing the outside dimensions of a combined rear-facing and forward-facing child restraint (see FMVSS 225, Figs 1 and 2) that is used by a vehicle manufacturer to determine the space required by child restraint systems in a given seating position and the location and accessibility of the lower anchorages in that position.

Child restraint system

A general term used in FMVSS 213 for devices designed "to restrain, seat, or position children who weigh 65 pounds of less." These include rear-facing restraints (infant-only and convertible), forward-facing restraints (convertible, child seat, combination seat), car beds, harnesses, and boosters (belt-positioning and shield). Any of these could also be designed and produced as built-in CRs, but currently only forward-facing systems exist. The standard specifically excludes vehicle belts (lap or lap-shoulder) from its definition. Common alternative terms are "child safety seat" and "car seat." The latter term should be avoided because of its likely confusion with "vehicle seat." (1/07)

Child seat

A common term for a CR that only faces forward and has an internal harness. All current models have a 5-point harness system. Most of the products of this type restrain children up to 40 lb with the harness and can then be used as a belt-positioning booster when the harness is removed (see also Combination seats). Some of these products are now designed to restrain children up to 80 lb with a harness, although they cannot be converted to a booster seat. For these higher-weight, harness-equipped seats, some require use of a top tether if the child weighs more than 50 lb. The minimum weight for a child using these CRs varies from 20 to 30 lb.

The advantage of this type of CR is that the harness slots are usually higher and the back usually taller than a convertible CR used forward facing, so they may better accommodate taller children under 40 lb who outgrow their convertible CR because of height. A disadvantage compared to convertibles is that they are typically more upright and have shallower side supports, which may be less comfortable for the child, particularly on longer trips. Some child seats can be reclined slightly, which can improve comfort as well as fit with the vehicle seat. (1/07)

Cinching latchplate - see Latchplate

Cleaning

Many CR covers are machine washable, while others can only be spot cleaned. Refer to the instructions. Buckles can be washed with mild soap and water and air-dried, but lubricants should not be applied to buckles. Harnesses can be washed, but soaking may leave the webbing stiffer than before, and bleach can weaken the material. It is sometimes not possible to completely remove the harness from the CR, so spot cleaning may be necessary. Do not remove webbing from latching or adjustment mechanisms unless there is a detailed threading diagram in the instruction booklet. Harness ends that are folded and sewn are not intended to be removed. For fabric covers, carefully follow the washing instructions provided by the manufacturer to retain fire retardancy.

Clip - see Belt-shortening clip, Harness retainer clip, Lap belt clip, Locking clip, Shoulder belt guide

Cocoon effect - see Tether, rear-facing

Combination seat

A forward-facing CR that has a removable harness and can also be used as a belt-positioning booster (see that entry for a drawing as a booster). For most products, this transition is made when the child reaches 40 lb. Other common names are "child seat/booster," "CR/booster," "child seat/BPB," or simply "combo." To prevent confusion, they should not be called convertible seats, which has another meaning, or highback boosters, since that only describes half of its function. Several manufacturers make two models with the same plastic shell: a combination seat with a removable harness and a BPB sold without the harness.

The advantages of purchasing a combination seat while the child is still under 40 lb are the higher back for head support and possibly higher upper strap slots (as much as two extra inches for some) compared to most convertibles, and the ability to convert it to a booster for use beyond 40 lb. A common error with these seats is that caregivers continue to restrain the child with the harness beyond 40 lb instead of switching it to booster mode. Manufacturers prohibit use of the internal harness and the lap-shoulder belt over both child and shell because of possible interaction between the lap belt and the harness buckle and between the shoulder belt and the harness retainer clip.

Combination seats come with top tethers for use in the child seat mode, and this tether should definitely be attached as the child approaches the maximum harness weight. Keeping the tether attached for the booster mode is not likely to affect crash performance, but it may be useful to stabilize the booster as the child climbs in and out, during vehicle turns, and to keep the tether hook contained. Check the manufacturer's instructions, which may advise removing the tether when the product is used as a BPB. Nearly all manufacturers state that LATCH lower attachments are not to be used in the BPB mode (check instructions for exceptions). Some say to stow them on the CR, while others say to remove the hardware and store it with the harness. These pieces must be replaced when the product is again used as a child seat. For more information on the use of lower attachments in the booster mode, see LATCH. (9/06)

Connector

Hardware at the end of a LATCH attachment, such as a top tether hook specified in FMVSS 213 or other latching device compatible with lower anchorages specified in FMVSS 225, that enables the CR to be securely fastened to a LATCH anchorage. Lower connectors can be either a hook-on type or a push-on type, where a spring-loaded latch automatically locks around the LATCH anchor bar.

Convertible child restraint

A CR that can be used rear-facing for infants up to at least 22 lb or as much as 35 lb, and then turned to face forward until the child reaches the product's upper weight limit, usually 40 lb. Most current convertibles can accommodate children rear-facing up to 30 lb.

Date of manufacture

The date that the product was completed at the factory. This date must be printed on the product itself, and the CR must meet all Federal requirements in effect on that date. A CR may be sold any time after the date of manufacture but does not have to meet any new requirements that become effective in the meantime. The date of manufacture is needed (1) to determine if the CR should be replaced because it is too old, (2) to determine if the CR is on recall, and (3) to order the correct top tether anchorage kit, if applicable. If the parent purchased the CR new and knows its approximate age, and there are no recalls in effect for that particular model, it is not essential to know the exact date.

There is no agreement on "how old is too old." At one time it was important to check that a CR was made after 1980, because 1981 was the year the Federal regulation requiring crash testing went into effect. Today, however, 1981 is not an appropriate point of reference for brochures and teaching materials, since CRs made that long ago should not be used anyway. Several years ago, Transport Canada issued a very reasonable statement, which others have adopted, that basically said that, after about 10 years, a CR is not likely to have all its parts and instructions nor have the important warnings and convenience features found on later models. There may also be some deterioration from heat and sunlight, but the validity of this concern has not been documented. See also Expiration date.

Dummy

Anthropomorphic (shaped like a human) test device specified in Federal standards, such as FMVSS 208 and FMVSS 213, to measure the protective capabilities of restraint systems in simulated crashes. The child restraint standard includes four dummies: Newborn (7.5 lb), P-¾ 9-Month (20 lb), VIP 3-Year (33.5 lb), and Hybrid II 6-year (47 lb). The air bag standard uses a different set of newer dummies: CRABI 12-Month (22 lb), Hybrid-III 3-Year (34 lb), and Hybrid-III 6-Year (51.5 lb). The most recently developed dummy is the Hybrid III 10-Year, which is expected to be used to test boosters and other products for older children. All dummies except the Newborn and 9-Month are instrumented, i.e., equipped to measure various accelerations and forces during testing. For complete descriptions and specifications of each, see the FTSS product catalog.

Emergency-locking retractor (ELR)

A vehicle belt retractor that locks when the vehicle stops suddenly, including sudden braking. It is activated when there is sufficient vehicle deceleration to allow a freely moving pendulum or, more recently, a ball-in-cup mechanism to engage and lock the retractor. Current vehicle retractors have an additional back-up feature that locks when the belt webbing is rapidly pulled out. After the tension is released, the belt can again be pulled out gradually. See also Switchable retractor.

Emergency tensioning retractor (ETR) - see Vehicle belt enhancements

Energy absorption

The transfer of crash energy to the permanent deformation of mechanical structures. This deformation can involve vehicle sheetmetal, padding that does not bounce back (such as expanded polystyrene), or an air bag undergoing controlled deflation. See also Ride-down.

Energy management loop (EML) - see Vehicle belt enhancements

Expiration date

In the last few years, CR manufacturers have been putting "expiration dates" on their products. This was begun in response to infant deaths from air bags. The companies realized that they had millions of products in use that said nothing about the danger to a rear-facing child. The concern became one that "best practice" and regulations change over time, so that a child restraint becomes "obsolete" and less effective than a new product, much the same way that medicines may change or become less effective after some time has passed. A current example would be with tethers--older CRs do not have them, and this is potentially a situation where a newer product will be more effective than an older one.

Taken at face value, the expiration interval (ranging from 5 to 8 years, depending on the manufacturer) is from the date of manufacture, which is what governs the labeling, certification, and other rules that apply. Whether to continue to use an "expired" CR is a judgment call, depending on the alternatives. It will work as well as before, but it is important to know what regulations and warnings may have changed and the risks involved. It is also important to take the expiration date into account when purchasing a CR that may have been manufactured several months or even a year or more before.

FMVSS 208

The U.S. Federal Motor Vehicle Safety Standard that establishes requirements for the protection of vehicle occupants in crashes by specifying limits on forces and accelerations measured on anthropomorphic dummies in test crashes, and by specifying equipment requirements for active (vehicle belt) and passive (air bag) restraint systems. See a complete copy of FMVSS 208 (PDF).

FMVSS 213

The U.S. Federal Motor Vehicle Safety Standard that establishes requirements for child restraint systems designed for use by children up to 50 lb in both highway vehicles and aircraft. These requirements cover crash performance, geometry, instructions and labeling, durability, flammability, and product registration. See a complete copy of FMVSS 213 (PDF). See also Date of manufacture, HIC, Head excursion, Height and weight limits, Instructions, Labels, Padding.

FMVSS 225

The U.S. Federal Motor Vehicle Safety Standard that establishes requirements for child restraint anchorage systems, also known at LATCH, in highway vehicles. These requirements cover the location and strength of the anchorages for effectively securing child restraints. See a complete copy of FMVSS 225 (PDF).

Forward-facing child restraint

A restraint that is installed so that the child faces the front of the vehicle. Current models may be a convertible, child seat, combination seat, backless child restraint, shield booster, or belt-positioning booster. See also Rear-facing vs. forward-facing.

Free-sliding latchplate - see Latchplate

Front seat use - see Seating position

Funnel guide

A device incorporated with some lower anchorages to help the user position and guide the lower attachment connector during CR installation.

Handle - see Carry handle

Harness

The webbing assembly attached to a CR shell or frame that restrains the child in a crash. It is equipped with a buckle, a method to adjust it snugly against the child, and usually a harness retainer clip. See also Harness types.

The term is also used to describe independent restraint systems made from webbing, connectors, and adjusters, but without a shell, that are often referred to as “child harnesses”. These products are typically recommended for situations where a standard CRS cannot be used, such as on school buses, when transporting older special needs children who need more torso support than provided by a three-point safety belt, and in lap-belt only seating positions where a CRS with higher weight limits cannot be used. Some harnesses attach to the vehicle with only a lap or lap-shoulder belt, while some also require use of a top tether strap. If used for a child over 48 lb, standard tether anchorages installed in vehicles may have to be replaced with a stronger anchorage. Child harnesses are tested according to FMVSS 213 to meet the head excursion limit of 32 inches and the injury criteria for the head and chest. Their use is prohibited on aircraft. (3/07)

Harness retainer clip

A plastic or fabric device that holds the shoulder straps of a harness in place on the child’s chest to achieve good pre-crash positioning. During a crash, the clip often is designed to either slide down the straps or separate if it has two parts. The harness clip should be placed at the level of the child’s armpits. For small babies, if there is not enough room above the buckle to position the clip at the armpits, a different CR should be used. The purpose of the clip is not to hold the child in the restraint, but to keep the shoulder straps in position, which is especially important if the harness is not adjusted snugly. Harness retainer clips are provided with most CR models in the US, but they are not permitted in Europe because of concerns about removing the child from the harness in an emergency.

A common problem at checkups is a missing retainer clip. Some CR manufacturers have stated that parts made by other companies should not be used with their products. However, instructions also state that the harness clip must be used. Technicians should keep a supply of clips from different manufacturers for use at checkups, to be used temporarily until parents can order the correct replacement clip from the CR manufacturer. (3/07)

Harness slot selection

For a rear-facing CR, use harness slots that are at or below the child’s shoulder level. In a frontal crash, the shoulder straps routed below shoulder level prevent the child from “ramping” or sliding up above the top of the CR, possibly resulting in head or neck injury for a larger child. If the lowest slots are above the infant’s shoulders in a convertible, try an infant-only restraint instead. For newborns, choose a restraint with at least three sets of slots, so the bottom slots are very low. If the lowest available slots are still above the shoulders, make sure the harness retainer clip holds the shoulder straps over the chest. Because of the child's short body and light weight, the risk of excessive ramping in this case is minimal.

For a forward-facing CR, harnesses should be routed through slots that are at or just above the child’s shoulders, which allows the child’s shoulders to immediately load the belt. For convertible CRs, caregivers need to check the instructions to determine which harness slots can be used forward-facing. On older convertibles, only the top slots could be used in forward-facing mode, because the lower slots were not reinforced to adequately restrain a forward-facing child in a frontal crash. If a harness is routed through slots that are not designed for forward-facing use, the shell may break out or the straps rip through the plastic, allowing excessive head excursion or even ejection (see photo). (3/07)

Harness strap cover

A padded fabric sleeve that covers harness straps at the shoulders. It is intended to prevent the edge of the shoulder strap from rubbing against the child’s neck. Some harness strap covers come with new CRs, while some are sold as accessories and may be longer than necessary. If they prevent the harness retainer clip from being properly positioned at the armpit, the covers should be removed or shortened. The fabric harness covers that come with a CR do not need to be used if the child does not like them. However, at least one CR manufacturer uses rubber sleeves over the harness straps to improve interaction between the harness and child. These cannot be shortened and should be used and positioned according to the manufacturer’s instructions. (3/07)

Harness tightness

A snug but comfortable harness is important for good crash protection, because the more tightly that occupants are belted, the more they can take advantage of “ride-down” with the vehicle. If there is a lot of slack in the harness at the time of a crash, the child first moves forward unrestrained but is then abruptly stopped by the loose straps. This can cause greater injury than if the straps were already snugly against the child’s body. NHTSA now requires that child restraint manufacturers include the following description in their instructions: "A snug strap should not allow any slack. It lies in a relatively straight line without sagging. It does not press on the child’s flesh or push the child’s body into an unnatural position." A common way to check that the harness is snug enough is the pinch test. After adjusting the harness so it is comfortable, try to pinch the harness webbing along its length (not its width). If you can grab some of the webbing, it is too loose. Some older guidelines state that there should be enough slack in the harness to insert one or two fingers between the webbing and child, but this measure is not as good because children’s bodies are soft and pliable.

When testing a 5-point harness (see Harness types), pull all of the slack from the lap part up into the shoulder straps before checking for tightness. If the harness does not touch the baby's body even when it is pulled as tight as possible, the problem cannot be solved for this model of CR. Such a situation can occur with small babies in some infant-only restraints and most convertible CR with shields. For distribution programs, staff should check for this potential problem before selecting the CR models they will provide to the public. Parents who already have such a CR should be encouraged to replace it (if new) or use a different model until the child is bigger. This is particularly important if the model has a shield (see Harness types). If there is a gap between the crotch strap and the infant's crotch, a rolled diaper or washcloth may be placed in this gap to help prevent slumping.

After adjusting the harness, be sure the strap length is locked in place. Many CRs have levers in front that automatically clamp the webbing, but tug on the straps to be sure. For rear-facing, be sure the lever is not caught in the "up" position against the vehicle seat. Also check that the connector hardware or stitched webbing in the back is not caught somewhere, leaving hidden slack. Some older CRs use a system where one end is sewn to a metal slide and the other end is free. Before adjusting the harness, the free end is threaded through the metal slide sewn to the other strap end. At this point, it looks like a buckle on a shoe. After adjusting the harness to the correct length, the free end of the strap must be looped back through the metal slide one more time to lock the webbing in place. When properly secured, the metal slide should look like a "C" (for correct), not like an "O" (for open). Another design has one end of the harness strap sewn to a metal slide, which must lie flat against the plastic on the back of the CR shell, in a location designated by the CR manufacturer. A common misuse is to have the end with the slide dangling, which introduces hidden slack.

Vehicle belts on children in belt-positioning boosters also need to be snug, but again not uncomfortably tight. The tension provided by the retractor may be adequate to keep the belt snug, but it is designed to allow some movement of passengers during travel. It may be necessary to lock a switchable retractor, if the shoulder belt does not stay properly positioned on a wiggling or sleeping child. Make sure the shoulder-belt guide attached to the booster does not grip the belt, preventing it from retracting after the child leans forward. (3/07)

Harness types

All CRs have a harness, a shield, or a combined harness/shield to directly restrain the child's body. There are several harness types. Safety experts recommend selection of CRs with 5-point harnesses unless circumstances require use of another type.

The 5-point harness (A) has a strap over each shoulder, one on each side of the pelvis, and one between the legs. All five come together at a common buckle. The function of the crotch strap is to hold the lap straps firmly down on top of the thighs, and it should be as short as possible. Because the crotch strap is merely a lap-strap positioning device, the actual restraint should come from the shoulder and lap straps. This type of harness fits children best, since the straps can be adjusted closely around the child's body, and the straps direct the crash forces at the child's strongest bony structures, the shoulders and pelvis.

The harness with tray shield (B), also called an "overhead shield," has shoulder straps attached to a curved plastic bolster, which is in turn attached with pivot arms to the sides of the CR shell and held down by a crotch strap and buckle. The tray shield was designed to take the place of the lap straps while being easier to use. Some harnesses can be removed from the shield for cleaning, but it is essential to re-connect the harness for the systems to work properly. Many parents perceive that the shield is more protective than straps, but this is not the case. In reality, the opposite may be true. This harness/shield system is not suitable for small babies, since it cannot be made to fit a small body tightly, and the shield may interact with a small child's neck or face. Some tray shields are adjustable, which improves fit somewhat. Tray-shield harnesses should only be used when the caregiver is unable to correctly use a 5-point harness system (e.g. arthritis in hands or other disability).

The harness with T-shield (C) has shoulder straps attached to a flat, plastic pad on a fairly rigid stalk that buckles into the shell between the child's legs. There are currently no products being sold in the U.S. that use this type of harness. This system does not fit babies well because the T-shield is not close enough to the child's body and is positioned on the chest or abdomen instead of the hips. For larger children, the bottom edge of the T-shield can uncomfortably press into their thighs.

Safety experts have concerns about CRs with shields. Tray shields are not usually covered with energy-absorbing padding to protect the head if it hits the shield. This contact is more likely with a shorter child and a loose harness. In a test series with a 12-month-size dummy, peak head acceleration was 35% higher for tray shield restraints than for 5-point harnesses. At least one child (19 lb) is known to have received a fatal head injury from contact with a tray shield. For T-shields, there is a concern that the throat of a small child may be injured from contact with the top of the shield during a crash. In the same series of crash tests, neck forces were 40% higher for T-shields than for 5-point harnesses, and the crotch load with T-shields was 2.7 times higher than with 5-points. See Weber 2000.

Most CRs currently sold in the US are equipped with 5-point harnesses, although some convertible restraints are equipped with a tray shield. In the past, infant-only restraints have had a “V-harness” or “Y-harness” where shoulder straps come together at a buckle in the shell or on a crotch strap. One infant-only safety seat even had a tray shield. (3/07)

Head excursion

The distance that the head of a child or crash dummy moves in the direction of impact or on rebound from a crash. Higher head excursions are associated with higher risk of head contact and injury. There are two head excursion limits for forward-facing dummies in FMVSS 213 testing. Before September 1999, the limit was 32 inches forward of a point located about 5 inches rearward of the seat bight. Since that date, nearly all forward-facing CRs have to meet an additional limit of about 28 inches (720 mm) from that point, but they can use a tether to do it. Retaining the old limit provides a guarantee that the CR is structurally sound and will perform as well as older models, even if the tether is not used.

Head Injury Criterion - see HIC

Heavy children - see Lap belts for children over 40 lb

Heavy-duty locking clip - see Belt-shortening clip

Height and weight limits

Manufacturers are required to label each CR with the child weight and height ranges for which the restraint was designed. This labeling determines the dummy sizes used to certify the CR. If a CR is certified for 22 lb or less, it must be tested with the Newborn and 9-Month size dummies. Certification to 40 lb requires additional testing with the 3-Year size, and over 40 lb requires the 6-Year dummy. Most CRs are certified with at least 2 dummy sizes, but those labeled only for children under 11 lb (a small car bed) or over 40 lb can be certified with a single dummy. When applying these labeled limits to a child, the maximum weight and the head position are more important than the standing height (or length) in determining when to move to a larger restraint.

Children should be weighed from time to time to anticipate when they are approaching the weight limit, and the additional weight of clothing is assumed. Tall, thin children will usually outgrow a CR before this weight is reached, but short chubby children may need to switch while they still fit in the harness and shell.

For rear-facing, the top of the child's head should be below the top of the shell, and a margin of at least an inch is recommended, so that the head will be supported and contact with the vehicle minimized during a severe crash. For forward-facing, the top of the child's ears should be below the top of the shell, to guard against neck injury (whiplash) in a rear impact. In addition, the child's shoulders should be below the highest strap slots to minimize slack in the harness. The only way to determine these height limits is to put the child in the CR and see if it fits. Note that many combination seats have higher strap slots than convertibles, even though they are both for children up to 40 lb.

Child restraint systems are engineered with a margin of safety, and they are tested under very severe conditions. It is therefore not necessary to move children out of their CR the moment they exceed either the weight specified or the recommended head or shoulder height. The concern is not that the harness or shell will break, but that, at some point beyond the limits, the CR will not provide optimal protection. The same applies to turning a convertible from rear- to forward-facing. However, with so many choices available today, it is a good idea to plan ahead for the next CR or belt system in time to get and install the best product for the child. This may involve installing a top tether anchorage or retrofitting the seat position with a shoulder belt.

HIC (Head Injury Criterion)

A calculated value indicating the likelihood of serious head injury, which may or may not involve direct head impact. HIC is computed using a complex formula related to the magnitude and duration of dummy head acceleration. Three of the child dummies (12-month, 3-year, and 6-year) used in FMVSS 213 tests measure head acceleration and can be used to calculate HIC. The maximum allowable HIC in FMVSS 213 is a value of 1000 and is based on adult injury tolerances. Many researchers believe the limit should be lower for child-size dummies, as they are when used in FMVSS 208 to evaluate potential air bag injury. (4/07)

Infant-only restraint

A restraint system that only faces the rear of the vehicle. Traditionally, these CRs have had an upper weight limit of 20 or 22 lb, but there are now some designs which accommodate infants up to 30 lbs. Most infant-only restraints are sold with two parts, a base and a removable shell. The base is kept installed in the vehicle, and the shell locks into the base. Extra bases can be purchased if the family transports the child in more than one vehicle. The shell has a handle that can be used to carry the infant outside of the vehicle. Caregivers should check instructions for infant restraints to determine the allowable positions for the handle during vehicle travel, which varies for each model. For most infant-only restraints, the shell can be installed directly to the vehicle without the base, although at least one infant-only restraint currently sold in the US requires the base for installation. However, regulations do not require removable shells of infant-only restraints to have LATCH lower attachments, only the bases.

Most infant-only restraints perform better in crash tests without their bases than with them, although the shell-only and shell-plus-base must both be tested to meet federal requirements. The flat-bottom base not only compresses the vehicle seat cushion more than the contoured shell, it also elevates the shell, raising the child’s center of gravity. The combination results in more downward rotation of the head-end of the shell and an increased risk of contact with the back of the front seat. There is also a chance that the shell could separate from the base in a severe crash, although recent base designs have reduced the likelihood of this happening. The base is a convenience feature and only improves protection of the infant to the extent that it may result in a more consistent and correct installation than would occur from reinstallation of the shell alone before every trip. (1/07)

Installation tightness

A tight installation improves the performance of any CR (see Ride-down), but it is not necessary or possible to make the system rigid. Installation should always include (1) compressing the vehicle seat cushion by pushing down on the CR, (2) removing all of the slack from the lap portion of the vehicle belt or the LATCH lower attachments, and (3) testing the lap portion of the vehicle belt to make sure it is "locked" against loosening (see Lockability, Locking clip).

When testing the installation tightness, grab the CR close to where the belt or LATCH attachment routes through the CR. If the CR can still be moved from side to side or toward the front of the vehicle more than an inch (see also Lockability test requirements), there may be a mismatch between the shape of the vehicle seat and the CR or between the belt path and the vehicle belt and/or anchorage geometry. For a rear-facing CR, it is acceptable for the top part of the CR to rotate toward the rear of the vehicle or to shift from side to side, as long as the CR is attached securely near the belt path (see also Top tether, rear-facing). For a forward-facing CR installed in a vehicle where the seatback is adjustable, tip the vehicle seatback rearward, install the CR, then bring the seatback forward. This may help provide a better fit between the CR and vehicle seat. If the installation is still loose, a different seating position or CR model may need to be used. For forward-facing CRs, a top tether should be used whenever possible, but this cannot completely make up for looseness of the vehicle belt or LATCH attachment. (9/07)

Instructions

CR manufacturers are required to provide printed instructions with diagrams for step-by-step installation of their products, positioning the child, and adjusting the system to fit the child. Various statements are also required about the consequences of not heeding the warnings on the labels, the dangers of air bags, the benefits of rear seats, and which vehicle belts to use with boosters. A storage location on the CR is also required. Refer to these instructions to find out minimum and maximum weights for which the CR is certified; how the harness is threaded, adjusted, and secured to the CR; how the angle of recline is adjusted; how to reassemble the CR correctly (after the harness has been cleaned, for example); the correct position of the carry handle; how to order missing parts; and other special characteristics of the CR.

CR advocates and technicians must have access to the manufacturers' instructions when advising parents. Since parents may not keep the instructions with the CR, it is necessary to have a set of all of the manufacturers' instructions (1981 through current date) on hand at checkup events. These instructions should be followed exactly, unless prevailing "best practice" has superseded the information provided in older instructions (see also Expiration date). An example would be to turn the child to face forward because the feet touch the vehicle seatback (see Rear-facing vs. forward-facing).

The instructions in the vehicle owner's manual take precedence over those of the CR regarding appropriate seating positions and the way the vehicle belts are used. For example, the CR instructions may state that an emergency-locking, lap-only belt cannot be used to install the restraint, but the vehicle manufacturer can provide a belt-shortening clip with instructions for a secure installation.

Integrated CR - see Built-in child restraint system

ISOFIX - A system for the connection of a CR to a vehicle that has two lower anchorages in a vehicle seating position located near the seat bight, corresponding rigid attachments on the CR, and a means to limit the forward rotation of the CR. The system was developed by an international standards committee and is expected to be adopted by European countries. ISOFIX differs from LATCH and LUAS with regard to the child restraint in that only rigid lower attachments are allowed, and for both CRs and vehicles top tethers are not required.

Labels

Manufacturers are required to label a CR with the model name or number, the date of manufacture, a statement that it "conforms to all applicable Federal motor vehicle safety standards," the weight and height limits for the child occupant, and various warnings about proper installation and use. Some of these must be visible when the CR is installed, which can be difficult when space is limited. There will be no label stating that the child restraint "passed" FMVSS 213 or is "approved." If the identification labels have come off or are illegible, the CR may still be good, but it will be harder to determine its name, how old it is, and if it has been recalled.

Lap belt clip

A piece of plastic to fasten the loose end of a manual (center) lap belt to the main part of the belt. If this clip makes it hard to pull on the tail to tighten the belt, it may be removed.

Lap belts and children over 40 lb

While using a lap belt is safer than riding unrestrained, there are now many better choices for restraining children over 40 lb, who have outgrown conventional CRs but do not have access to a lap-shoulder belt in the rear seat to use with a belt-positioning booster. There are now several convertibles, combination seats, and child seats available to accommodate children who weigh up to 80 lb. In addition, there are special needs CRs that fit larger children. These seats are typically among the more expensive CRs, and they are also bigger than other child restraints, which may prevent installation of another CR or booster in an adjacent seating position. There are also several harness and vest alternatives for larger children. For a current list of all these products, see “Booster Seats and Other Products for Children Over 40 Pounds,” bottom of p.1. Using the top tether is especially important with heavier, taller children in these larger restraints. Likewise, belt-positioning boosters should not be used with lap belts alone, because raising the child, together with the absence of an upper torso restraint, increases the likelihood that the child’s head will contact the vehicle interior during a crash. (7/06)

LATCH

An acronym that stands for "Lower Anchors and Tethers for CHildren" and refers to the child restraint anchorage system specified in FMVSS 225 and corresponding top tethers and lower attachments identified in FMVSS 213. The system includes lower anchorages in the form of rigid bars installed in the vehicle seat bight and flexible (A) or rigid (B) lower attachments on the CR that connect to the bars. LATCH has been phased into the vehicle fleet, but all passenger vehicles made from September 2002 must have the system in a certain number of seating positions. LATCH is also required on child restraints (with a few exceptions) manufactured from September 2002 and is available on many models made before that date. The exceptions include car beds, child harnesses, and belt-positioning boosters.

The LATCH system allows you to securely attach your safety seat in your car without using the vehicle belt and possibly to get a better fit. For seating positions with LATCH anchors, experts recommend trying the LATCH installation first and only using the vehicle belt in that seating position if LATCH, for some reason, results in a looser fit. If you want to use the center rear seat and no LATCH anchors are available (check the vehicle owner's manual), try the vehicle belt to be sure you can get a tight installation. If you cannot, try the LATCH anchors in a different seating position.

When a combination seat is used in the booster mode, most manufacturers instruct the parent to remove the LATCH attachments from the CR, or at least the lower ones, and store them with the harness. This is primarily due to the weight limitation on highback boosters, which is usually exceeded with the addition of the LATCH hardware. The complication is that the lower attachments are supposed to be "permanently attached," so other manufacturers instruct that LATCH be detached from the vehicle anchorages and stored on the booster itself, often putting the booster over the weight limit. This aspect of booster regulation and practice is currently in transition. NHTSA has recently said it is not enforcing the 9.7-lb weight limit on boosters that could impose loads from behind and push the child into the belt. Since manufacturers are not required to test booster performance with LATCH, they are reluctant to recommend it, even though such usage would isolate the booster from the child and thus get around the booster weight limit. Expectations for the future, however, are that combination seats and highback boosters will become heavier, a higher weight limit will be established, and other systems such as lock-offs and LATCH will be used with boosters.

For further details, go to the Safe Ride News LATCH Primer, our summary of LATCH requirements, and NHTSA's Tips on Installation and other FAQs. For a comprehensive manual, see SRN's LATCH...An Essential Guide.

LATCH anchorage – Hardware in the vehicle to which a top tether or a lower attachment is connected as part of a complete CR installation.

LATCH attachment – A hardware assembly on a CR, possibly including webbing, that connects to a top tether anchorage or a lower anchorage as part of a complete CR installation. See also Connector.

Latchplate

The metal portion of the vehicle belt assembly that connects to the buckle and through which the webbing is threaded. The insertion tip is also called the buckle "tongue." For lap-shoulder belts, there are "locking" and "free-sliding" latchplates. The locking type will allow the lap portion to be pulled into the shoulder portion but will restrict its slippage back to the lap belt. The free-sliding type allows the belt to slip easily in either direction. A third "cinching" latchplate will hold the belt enough to meet the requirements of the lockability standard but will allow the belt to slip through the slot during a crash. Another variation is the "switchable" latchplate available on a few vehicles. It is normally free-sliding but can be made to lock the belt by moving a dial or button to the "child" position. Lap-only belts also have locking latchplates that restrict slippage once the belt is pulled tight. To hold the locking bar in place and remain tight, however, the webbing must be parallel or nearly parallel (angle of less than 30°) to the latchplate. See also Lockability and Twisted vehicle belt.

Load limiters - see Vehicle belt enhancements

Lock-off device

A clamp attached to the CR that is affixed to the vehicle belt to perform one or more of the following functions: (1) prevent movement of the belt relative to the latchplate, (2) maintain an applied tension on the belt from the floor anchorage through the latchplate to the lock-off, and (3) prevent movement of the CR relative to the belt webbing. If performing function (1), the lock-off replaces a locking clip. If performing function (2), it does not replace a locking clip but eliminates the need for one. It is still useful to lock the switchable retractor, if this feature is available. Function (3) is intended to improve ride-down and pre-crash stability by keeping the CR from sliding relative to the lap portion of the belt, but this lock-off usage does not fix the lap belt length or maintain belt tension. Function (3) does not replace a locking clip or the lockability feature of the vehicle belt.