Are Car Seats with Seat Belts and Lower Anchors Safe?

child car seat in back of car
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Today, children's car seats can be installed with a seat belt or the Lower Anchors and Tethers for Children (LATCH) system. Parents who want an extra measure of security might mistakenly think that they should install their baby's car seat with both a vehicle seat belt and the anchors and tethers of the LATCH system.

It's easy to see why some parents believe that if one strap holding the car seat into the car is good, two straps holding it into the car must be better. However, using two installation methods doesn't necessarily add an extra layer of protection and can be an unsafe decision.

The LATCH System: Anchors and Tethers

The lower anchors are metal U-shaped or horizontal bars that can sometimes be hidden inside your vehicle's seat crease (or be visible sticking out from the crease). You'll find two sets of lower anchors—one on the driver side and the other on the passenger side in the back—in most vehicles.

The tether anchor is the second part of the LATCH system in your vehicle. It can look like the lower anchors, but remember that there's only one per set of lower anchors.

Why You Can't Use the Seat Belt and LATCH

Car seats are designed to handle crash forces in specific ways. Thanks to federally mandated crash testing, we know that a baby's car seat will withstand crash forces when installed with the seat belt or with the anchors and tethers of the LATCH system. However, we do not know if the same car seat will withstand crash forces when all components of both systems are used at the same time.

There are several reasons that installing both systems is unsafe. For one, putting two installation belts through the same belt path could put stress on the car seat shell from two different angles during a crash, which could cause breakage.

Additionally, using two installation belts could concentrate more crash forces on a small area of the car seat, which in turn could cause it to move or fail in ways that cannot be easily predicted.

The rule of thumb to follow with installation is to never use your baby's car seat in a way that was not intended by the manufacturer.

If you install the car seat using methods that are not outlined in the seat's instruction manual, it's like you're using your child as a crash test dummy. You can't be sure of what will happen when car seats are used in ways that have not been crash-tested and approved. To find out how your car seat should be installed, check the car seat instructions as well as your vehicle's owner's manual.

If you cannot get the car seat installed tightly using either the vehicle seat belt or the components of the LATCH system, find a certified child passenger safety technician or a car seat inspection station by visiting Safe Kids USA.

Which Installation Method Is Best?

You should choose the installation method that allows you to get the best fit for your vehicle. A car seat is installed correctly when you cannot move it more than an inch in any direction when you grab the car seat at the belt path. After verifying that the seat is tight, make sure it is angled properly—reclined for rear-facing kids and more upright for forward-facing kids.

Remember that even though you have to pick between the vehicle seat belt or the lower anchors (part of the LATCH system), the tethers are used in addition to the vehicle seat belt or lower anchors for every forward-facing installation.

You also need to keep in mind that the lower anchors of the LATCH system have a weight limit. You will need to switch to a seat belt installation once your child reaches the weight limit and the lower anchors can no longer be used.

The lower anchor weight limit is listed on the car seat labels and in the instruction manual. It's best to learn both installation methods right from the start. That way, you're prepared for any vehicle switches, too.

Currently, there are several seats that do allow the use of the lower anchors and seat belt simultaneously. Carefully review the information on the product you've purchased to ensure you understand how to install it safely.

As of 2020, all of the seats that allow lower anchors and seat belts at the same time feature rigid LATCH (which is a safer installation method than a lower anchor strap or a seat belt) and no lower anchor strap.

However, it's important to keep in mind that car seat safety information can change quickly as manufacturers put out new seats.

Always read that instruction manual—even if you think you're already very familiar with the car seat model. Some of the updates might apply to newer versions of the same car seat.

What About Booster Seats?

The lower anchor weight limits only apply to car seats (where the child is restrained by a 5-point harness). Lower anchor weight limits do not apply to boosters (boosters are seats where the child sits on the booster and uses the vehicle's seat belt across them as the restraint).

Many booster seats can connect to the vehicle's lower anchors. It is safe for the booster to be secured to the lower anchors while the child is secured using the vehicle's seat belt across them.

Boosters are positioning devices and do not take much (if any) of the forces in a crash. Car seats, however, are the restraint for the child and take a great deal of force in a crash, as well as pull tremendously on the lower anchors in the vehicle.

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