I really liked the brake-boost mechanic. It made me feel like I was playing Crazy Taxi: Front Lawn Edition. The decision to do all the linework in the art with that rough pencil brush was a great choice too. It really drove home that "simple, fun flash game" art style you have going on. In fact, the whole game felt like it would've been right at home on Newgrounds circa 2009, and I mean that in the best way.
Great work :)