The GMC PD-4501 Scenicruiser, manufactured exclusively for Greyhound Lines, was a three-axle monocoque two-level coach used by Greyhound from 1954 to the 1970s. It was introduced in July 1954, and in total, 1001 were made between 1954 to 1956.
Due to its ubiquity in US cities and along highways in the late 1950s and the 1960s, the Scenicruiser became something of an icon of the American way of life of those years.
The high-level design concept of Scenicruiser may have been inspired by the passenger-carrying railroads of the United States and Canada and their popular dome cars; however, this type of two-level body in motorcoachs was common already in the late forties in Western Europe, including Great Britain where it was known as Observation coach. Actually the concept of two-level monocoque body was already present in the Spanish Pegaso Z-403 two-axle coach, designed in 1949 and in production since 1951.