From the Bewitched episode, "How Green Was My Grass", Samantha demonstrates a 1968 children's car seat, where a single bar is pulled over into place. The car seat is hooked over the front passenger side.
By 1971, Tabitha was a grown woman of age 5 and no longer needed a car seat. Adam used one, in the middle of the front seat. He is sitting quite high and has a great view of the road.