Can I use both the vehicle seat belt and LATCH strap at the same time?
No, you must not use both the vehicle seat belt and LATCH strap at the same time when installing the car seat. Both installation methods are equally safe, but you must choose one method or the other.
From the official Graco Tranzitions Car Seat manual, page 7
Have a follow-up question?
Answers from the official manual.
Common questions