Feels like this has a lot of potential without quite being there yet:
The gameplay's quite fun, and I think I'd enjoy playing it with a friend, except for a couple of things. Like- if the cars leave the screen, you can't see either of them and it's pretty much game over (the old game Micro Machines has the best way of solving this problem)
Also, adding sound, a main menu and spending more time on the graphics would go a long, long way to improving this.