A: First of all, I'm glad to hear that your son is rear-facing even after outgrowing an infant car seat. That's a smart choice, and extended rear-facing is recommended by more baby safety experts every day.
The car seat top tether can sometimes be used in the rear-facing position, but only for a few car seats. You need to check your car seat instruction manual to know whether your car seat can be tethered rear-facing. When it's time to turn your baby around to forward-facing, you should use the top tether anytime the vehicle has an anchor for it. The top tether, when properly used, reduces the forward motion of your baby's head in a crash. Less head movement results in fewer severe injuries to the head and neck.
The top tether is actually part of the LATCh system. In fact, LATCh stands for Lower Anchors and Tethers for Children. When you install a car seat forward-facing with the LATCh system, use of the the top tether is required. If you have installed a forward-facing car seat with the vehicle seat belt, use of the top tether is optional but highly recommended if anchors are present.
In your vehicle, the top tether anchor can be tricky to find. Some vehicles have a tether anchor on the back dashboard, while others have tether anchors on the floor behind rear seats or even on the ceiling in some SUVS. Vehicles manufactured between 1989 and 2000 often have pre-drilled top tether anchors, so you can take your car in to a service center and have the anchors installed. Vehicles manufactured after 2000 usually have top tether anchors already installed.
If your vehicle doesn't have a top tether anchor, or you can't use the tether rear-facing, be sure to secure the tether strap so it can't fly over and hit your baby in a crash or a sudden stop. Most car seats have a specific place to secure the tether's hook, so check your car seat instruction book to find out what the manufacturer suggests.
Heather Corley is a certified Child Passenger Safety Technician.