A 3rd installment of the Flatout series has been released!
It looks about the same as 2, but includes the ability to race 15 other players and demo derby with 23 other players.
According to the devs, they did allow a LAN mode (called private)...but it does require initial authentication with steam.
I purchased and played...very happy right now.
http://store.steampowered.com/video/201510/81307