In the early 80's, my cousin was involved in an accident. (Right at sundown, driving west, he turned in front of another car. Technically, he was at fault, but the other driver did not have his lights on, so he was not ticketed.) The other car had a three year old asleep in the back seat. He was thrown into the floor, but unharmed. Unfortunately, his 9 month old sister was not so lucky. Mom was holding her in the front seat, and not wearing her own seat belt. She held on to the baby, but sadly hit the dash and crushed the baby, who died instantly.
The same year, a friend of mine and her husband and daughter were hit head on by a semi that went the wrong way down a divided highway. She and her husband were killed, but their baby girl survived. The baby was strapped in a car seat, between her parents on the seat of a pickup truck. The baby went through the windshield in her car seat, and except for minor cuts on her face, the car seat still protected her.
My kids always believed the car wouldn't start until everyone was strapped in.