There was a video a while back about a new Driving Physics and crash modeling sim froma company called BeamNG. Well now there is a tech demo available and you can purchase alpha access (with all future upgrades including retail ala Minecraft). I purchased the alpha access as this looks to be a great driving sim.
So far it has been pretty fun driving around the maps given. you can also edit the maps they give you and if you are especially technical with modeling software I believe you can make a new map completely from scratch. I haven't delved into the editor as of yet.