Based on the TV show of the same name, as seen on the Discovery Channel, this game allows you to customize and race motorcycles.
There are a variety of challenges available, from regular races, to free-roaming city driving (featuring plenty of regular traffic to work around).
The game has you be the "new guy" on the show; the Teutuls (voiced by the actual people from the show) send you on the various missions. Each mission features several goals, some mandatory while others are optional. Completing the goals unlocks new motorcycles and parts.