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.
A sleeping baby. A baby is a very young human who is born after a mother gives birth. A baby is called a newborn for the first 1 to 3 months of life. They are then called a child until about the age of three years old, and a preschooler between 3 years old and school. An infant is a human child at the youngest stage of life.