I created a small video of my game for all the people who don't want to invest their time in downloading and testing the game I supplied in my previous post for whatever reason:
Often I have more time to simply comment on things and less time to actually work at something. I tried downloading and running your prototype last night but received an error regarding some DLL (which sounded related to Ogre). I'll give you an exact copy of the error when I can.
Looking at the video, however, I REALLY like the aesthetic of the car movement design. It would appear to be fluid enough to use without slowing down the player significantly.
Some of the controls appear limited, however, at least based on what you use in the video: changing velocity appears to be key-based while selecting a direction appears to be mouse-based. Ideally you'll want to be able to control all movement in the car with either or.
I also noticed that there are a rather large number of options to move, which could potentially make key-based movement rather convoluted. At the most, I was expecting seven distinct motions per velocity: forward, lean left/right, soft-turn left/right, and hard-turn left/right (where soft-turn is the full motion and soft-turn is for roads), which the exception of moving backward instead of forward when the car is in reverse. For some reason there's always two squares for forward, which isn't necessary if speed changes are handled separately; there are also some rather sharp leans, which I wouldn't expect a car to handle very easily; for soft/hard turns at speed 1 there's no noticeable difference, but when including leans, you have spaces that act differently depending on the orientation of the car. All of this depends on how you want the cars to move, though, so take it only as a consideration.
I'll try to give better feedback once I can get the prototype to run myself.