Okay, not too bad
Now, The Cars' Physics need touching up, things like being able to drive up steep gradients, and the rather cartoony handling. I'm not sure of the capabilities of this within unity, and I am guessing you won't be able to make it realistic no matter how good you are.
Because of this, you want to give your game a strong theme to match the arcade handling. Think of games like mario kart (as terrible as it is) for reference. Their poorer handling (although why professionals can't make the cars handle is beyond me) is made up by a strong theme and great game mechanics. You should decide how you will make up for somewhat unrealistic handling
As a base for a game, quite impressive, and it pokes above the usual bunch at 6/10
I love Cheese; It Fills Me With Glees,
My Tastebuds it please; oh yes, i love cheese.