This is a sub-page of The Simpsons: Hit & Run/Unused Vehicles.
Although technically not unused, as mods can bring them back up or an in-game cheat for the phone booth makes a subsection for these cars, and the fact that they are used by NPC racers in the bonus racing mini games, the following cars are never seen on the roads and cannot be purchased. Oddly, for unused cars, they can be driven by the player and have proper statistics like normal cars, hinting they were originally going to be used at one point in the game.
Additionally, there is a Test.con, a testing handling file for a "ferra".