Is it safe to recline the seatback while the vehicle is moving?

No, sitting in a reclined position while the vehicle is in motion is dangerous, even when wearing a safety belt. In a reclined position, the shoulder belt will not be against your body and the lap belt could ride up over your abdomen, causing serious internal injuries in a crash. Always have the seatback upright and sit well back in the seat when the vehicle is moving. (Page 12)