I have never heard of this expression before but I'm guess it refers to the fact that nowadays trains use digital signals instead and as a result they don't have caboose/brake van anymore. So (without context), it probably means that the person who said it believed that caboose is important and safer than digital signals? Or the trains will be safer to have a live human being watch out for it ?
Definition of baby. plural. babies. 1a (1) : an extremely young child; especially : infant (2) : an extremely young animalb : the youngest of a group He is the baby of the family.
C2 [ C ] a baby or a very young child: a newborn infant. More examples. She has five children, the youngest of whom is still an infant. He was very unwell as an infant, and was not expected to live into adulthood. Separated from his mother when he was just an infant, the boy grew up in a children's home. She isn't able to look after herself at all - she's as helpless as an infant.