Can I use both the LATCH system and vehicle seat belt at the same time?
No, you should not use both the LATCH system and vehicle seat belt at the same time. Both are equally safe to use, but DO NOT USE BOTH AT THE SAME TIME. Choose one installation method for your child restraint. (Page 7, 22)
From the official Graco Tranzitions XP Proportioner manual, page 7
Have a follow-up question?
Answers from the official manual.
Common questions