So apparently UP had these. Description about these “things” Union Pacific M-10000: Built in 1934, Union Pacific's M-10000 was the first lightweight articulated trainset built in the United States. The all aluminum carbody, built by Pullman, weighed only 85 tons for all three units. That's about the same weight as a single heavyweight sleeping car. The 600 hp engine was made by Winton. Design and construction were overseen by Electro-Motive Corporation. These two companies were soon thereafter combined by parent General Motors to form EMD, and M-10000's distinctive turret cab design evolved into the famous nose profile of the EMD E and F series diesel locomotives. However, Winton had not yet perfected a reliable diesel engine when the M-10000 carbody was ready. Thus EMC and UP elected to install a 12 cylinder "spark distillate" engine, similar to ones EMC had been using for years in heavyweight railcars. Petroleum Distillate is a by-product of the refining process, with a formula somewhere between gasoline and diesel fuel. In 1934 a gallon of "PD" cost 3¢, as opposed to 15¢ for gasoline. The M-10000 also introduced "Armour Yellow" as one of UP's signature colors. Named after the color of the refrigerator cars owned by the Armour meat packing company, this same color is still used on UP diesels, 67 years later. The "Leaf Brown" trim color was replaced by "Harbor Mist Gray" in 1941, but the body color and the red separating stripe mark this as the origin of the longest-lived paint scheme in US railroad history. Built primarily as a testbed and publicity tool, the M-10000 was assigned to the short route from Kansas City, Missouri to Salina, Kansas. When assigned to that service, it was given the name City Of Salina, the first of UP's "City Of" trains. M-10000 was scrapped in 1942, because its distillate engine could no longer be economically maintained. Though not as famous as the later, diesel powered, Budd built, Pioneer Zephyr, UP's City Of Salina was America's first of a long line of lightweight, modern trains.
banksofthesusquehanna.com for the Union Pacific M-10000 train set and basic info on it Wikipedia for the poster and the info (type and origins, and specifications)
