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.
Definition of infant for Students. History for infant. To the parent of a crying infant unable to say what the problem is, the etymology of infant might seem very appropriate. In Latin the adjective infans literally meant ânot speaking, incapable of speech.â The noun infans referred to a very young child who had not yet learned to talk.