Forza Horizon is a cross between TDU or NFS and Forza. Open-world / free-roam style game set in Colorado, with the Forza physics engine and car models. With all driving assists on it is supposed to play like any other arcade racer; turn em off and it's normal Forza sim-style racing.
First real attempt to make an open-world racer with (the capability of) sim-racing driving mechanics.
ETA: Behind the scenes video
This post was edited on 9/27 at 12:17 pm