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.
preemie, premature baby, premature infant, premie, preterm baby, preterm infant - an infant that is born prior to 37 weeks of gestation. SGA infant, small-for-gestational-age infant - an infant whose size and weight are considerably less than the average for babies of the same age.