Just a quick suggestion, feel free to remove this if it's in the wrong place.

I think it would be beneficial to change the way the handbrake works. Instead of locking and staying on when the button is pressed, why not just have the handbrake engage while the button is pressed, and release when the button is released.

This would be good for starting races, doing 180's, etc...

Loving the prologue so far, its got a great driving experience, and aesthetic. The Map is a little confusing, but see that's been mentioned in other posts.