1997 GMC Suburban Owner's Manual - Page 15

I But don't have a seatback reclined if your vehicle is moving. Sitting in a reclined position when vehicle is your in motioncan be dangerous. Evenif you buckle up, your safety belts can't their jobwhen do you're reclined like this. The shoulder belt can't do its job because it won't be against your body. Instead, it will be in front of you. In a crash you couldgo into it, receiving neckor other injuries. The lap belt can't do its job either. In a crash the belt couldgo up over your abdomen. The belt forces would be there, not at your pelvic bones. This could cause serious internal injuries, For proper protection when the vehicle is in motion, havethe seatback upright. Then sit well back in the seat and wear your sa.fety belt properly. . 1-5