Two almost forgotten "rocket trains" are in the Railway Museum of Pueblo (Colorado). From Grumman comes the Tracked Air Cushion Research Vehicle, which was tested in 1972. As "The Tube" was the UTACV (Urban Tracked Air Cushion Vehicle) called, which was intended for passenger transport. The only prototype dates from 1974. Both were actually jet-powered hovercraft, which ran on special rails. The tests did not meet the expectations, the projects were too expensive (own rail network necessary) and the vehicles also too loud. So the two are now museum pieces.