They came in packs, with a small track. You rolled dice and raced your car against your opponent's car. I have no clue if it was at all realistic. I highly doubt it.
Although I purchased a pack or two many years ago, I never actually played it. I did assemble the #20 Home Depot Tony Stewart. It still sits on my bedroom window sill.
The game had two seasons, 2005 and 2006. Then WizKids discontinued it. From what I understand they have removed all references to the game from their website. More info can be found at Board Game Geeks.
Collectible? Sure. Is there really a market for this stuff? Probably not.