The Collaborative International Dictionary
Observation car \Ob`ser*va"tion car\ A railway passenger car made so as to facilitate seeing the scenery en route; a car open, or with glass sides, or with a kind of open balcony at the rear.
Wikipedia
An observation car/carriage/coach (in US English, often abbreviated to simply observation or obs) is a type of railroad passenger car, generally operated in a passenger train as the last carriage, with windows on the rear of the car for passengers' viewing pleasure. The cars were nearly universally removed from service on American railroads beginning in the 1950s as a cost-cutting measure in order to eliminate the need to "turn" the trains when operating out of stub-end terminals.
The push-pull mode of operation removes this limitation. In Europe, various trains are now fitted with observation cars at either or both ends.
Usage examples of "observation car".
There were four tables reserved in the rear of the dining car for the occupants of the observation car.
The observation car had been parked opposite the Central Post Office in Station Square for less than fifteen minutes, but already Philipson had to keep wiping the windscreen to clear the mist that was freezing - he rubbed now with his heavy mitten until a scratchy little patch of clear glass allowed him to check that it was Captain Ozeroff entering the glass doors of the post office.
Art and Linda drank ginger beer in the observation car, spiking it with rum from a flask that Linda carried in a garter that she wore for the express purpose of being able to reach naughtily up her little sundress and produce a bottle of body-temperature liquor in a nickel-plated vessel whose shiny sides were dulled by the soft oil of her thigh.
When nearly all the passengers (including Filmer) had left, heading for their own rooms or the observation car, we cleared the tables, spread fresh cloths and began thinking of food for ourselves.
Maybe we'd better go down to the tracks and see if any more packages come sailing off the observation car.
Behind him panted a steam locomotive drawing a single observation car.
As I dressed in the mirror that night, I suffered the hard-edged conviction that someone else was wearing my sleeve and that I had been reduced to the role of a passenger in the observation car behind the eyes.
A train of boxcars, tank cars, and gondolas stopped to give right-of-way to a diesel speeding through with passenger coaches and an observation car.