What too look for when choosing a safety seat for your child:
Some seats are wider than others, so be aware of your needs when choosing a seat. Some don't “play well with others” in 3-across situations. Also, sometimes overall width isn't as important as the shape of the seat. Some fairly wide seats will fit together like puzzle pieces. When it comes to fitting three seats across, often a family has no choice but to experiment. A helpful site to weed out what may or may not work is: www.carseatdata.org
Infant (carrier) Seat:
Harnessed (convertible) Seat:
5 point harness
Front harness adjustment- High rear-facing weight limit (33 pounds or higher)
- Tall seat shell
- High forward-facing weight limit (anything above 40 pounds is excellent)
- Tall harness slots
- Ease of use features such as built-in lock-offs and/or “alligator”-style LATCH connectors
- Engery-absorbing foam
- Side Impact protection
- Removable/replaceable covers for easy clean up
- Padding
- Width (more of an issue if you are attempting to fit three seats across one row of your vehicle.)
Avoid 3-in-1 seats, generally they are "jack of all trades, master of none" and rarely meet a family's needs effectively.
Forward-facing only:
Tall harness slots, shell and high weight limit
Be aware of limitations, some have special requirements
Avoid combination boosters with closed belt guides for booster mode.( These are seats with an integral 5-point harnessed that can be removed for use as a belt-positioning-booster.)
Width if you're attempting three-across
Engery-absorbing foam
Removable/replaceable covers for easy clean up
Belt Positioning Booster Seat:
Some high-back boosters require support from the vehicle seat and are not appropriate for older vehicles lacking head support. Be sure and read your manual!