 The resulting report was published in 1968 and proposed the development of PRT, as well as other systems such as dial-a-bus and high-speed interurban links.In the late 1960s, the Aerospace Corporation, an independent non-profit corporation set up by the US Congress, spent substantial time and money on PRT, and performed much of the early theoretical and systems analysis.However, this corporation is not allowed to sell to non-federal government customers.