General Motors' Aerotrain, introduced in 1955 as the future of American passenger trains, didn't have a very long future, despite its futuristic design.
For one thing, it arrived in an era when passenger rail service in the U.S. was departing; for another, its lightweight design made it rough-riding and uncomfortable and for yet another, the streamlined locomotive was an underpowered switch engine in disguise.
Although GM was a major locomotive manufacturer in those days, design of the Aerotrain came from the designers of its cars, and the passenger cars were based on the design of GM's then 'new look' buses (in fact, they were also the 40' length of buses, half that of normal train cars).
The Aerotrain was built as a trainset, semi-permanently coupled. GM built two of them, and lent them out to railroads to try out and (hopefully) place orders. Over the next couple of years, they ran on the Pennsylvania Railroad, the New York Central, the Rock Island Line, Santa Fe and Union Pacific, among others. None of them was impressed enough to order any, and in the end, GM sold the two demo sets to the Rock Island, which used them in commuter service for ten years.
The title image shows one partial set at the National Museum of Transportation in St Louis, a fabulous museum of cars, trains, buses and even a plane.
Despite its lack of success as a train, the design survives as the Zooliner, a small-scale train running on the Washington Park and Zoo railroad in Portland, Oregon.