GM Aerotrain

https://www.american-rails.com/aero.htm ... OuY73Gi4NU

GM's "Aerotrain"
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The company had a very good idea, which was envisioned by its vice president of styling, although it seems not enough research and development was spent on the train.

Its general problems included a rough ride and under-powered locomotive. As a result, not a single railroad ordered a trainset despite extensive testing on both the New York Central and Pennsylvania. They were eventually purchased by the Rock Island and used in commuter service until 1966.
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The first concepts for what became the Aerotrain appeared to the public in the June, 1955 issue of Look Magazine.

At first, it was described as "Train Y" to readers and the article looked to awe them by stating that it could operate at speeds greater than 100 mph and be able to connect New York and Chicago in 10 1/2 hours or run along the NYC-Boston corridor in just 2 1/2 hours.
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"Look" was a fine magazine, but hardly a technical journal: doubtless the powers that were at GM were happy to get a puff piece in a mass-circulation mag!
Speeds over a hundred mies per hour are all very well and good, but don't translate into very short end-to-end times unless they can be maintained: "Train Y" might have ben fast Chicago to Buffalo, or even to Albany, but the last leg of the trip to New York, down the Hudson, has lots of curves (as does the New Haven's "Shore Line" route from Boston to New York). Maintaining speed through these curves... (And regaining speed after a reduction would have shown up the inadequacy of the power.)
The name "Train Y" is interesting. Sounds like a deliberate comparison being made to the competing "Train X". Train X was the ancestor of the United Aircraft "Turbo Train" of the late 1960s and 1970s: that one had tilting cars, which would have made it more able to cut timings on routes like the Shore Line or the Hudson Valley.
(And: thank you for posting the link!)

Skimming the article: interesting that the New York Central tried out "their" Aerotrain on the Cleveland to Chicago route: the Centra's staff, as railroad professionals, saw that the Aerotrain, with its low power and non-tilting cars, was suitable only for straight and level track.