An ETV (emergency transport vehicle) was a type of high-speed Federation space vessel used to ferry high-ranking personnel when a starship was not available. (NF novels: After the Fall, Blind Man's Bluff) This would seem to have been the function of a few other vehicles, including the shuttlecraft NCC-1696/8, and the warpshuttles Surak and Golden Hind, both of which were SW7-class craft with warp sleds, with two and three warp nacelles, respectively.