The last car in the train was the caboose for many years. Is that what you were referring to? I don't know of any other name for a small platform at the back of a rail car. Politicians would stand on the back platform of a normal car when touring the state or country while running for election many years ago. But I am not aware of any special name for the platform of a railroad car.
I think it's known as the verandah, borrowing the architectural term.
Platform
The outside of an egg is called the shell.
Each part of a train is called a car.
The engine. The driver is called the engineer.
rim
The very outside part of a black hole when "feeding" is called the Accretion Disc. when a black hole is not devouring a star the outside part becomes the Event Horizon.
Platform is a noun.
you see the out side of it which is called the base or the outside
margin
If it's a powered locomotive, then a locomotive. If it's a car with a cab to control the train, then a cab-car. If it's a train powered by itself, called a Multiple Unit (MU) with the engine part of the train, the front is called, well, the head end.
The last part of a train is a caboose.
Quand part le train? Quand va le train partir? Le train part a quelle heure? Quand est-ce que part le train?