Trial by Dirt is a two-lap checkpoint mission with no time limit. To complete this mission, the player must clear each checkpoint without destroying their bike or dismounting too long from it. There is a health pickup nearby on the track, in case Tommy falls off and gets injured. The course is essentially the reverse of that of Test Track (which is activated by entering the Landstalker spawned by the Sanchez instead).
The player can keep playing this mission once they've completed it. An additional challenge is added each time the player beats their record:
- After setting the first record, four explosive barrels are placed on the last stretch of the track.
- After beating their first record, rain will begin to fall by the second lap, making the track slippery to the player's vehicle.
- After beating the record for the second time, three hostile Haitians armed with Machetes and riding uniquely black Sanchez's will spawn on the track and pursue the player without concern for the track's layout.
Completing the mission for the first time rewards the player $100, and accumulates an additional $100 each time the player beats the mission's record time.
- Due to a bug in the game, the initial scores of both Trial by Dirt and Test Track will have the same time once both scores are listed in the statistics. Once both missions are played again and each time is beaten, the scores will be individual as they should be.
- If player completes Trial by Dirt before Test Track, the Test Track's time result will not show up in stats screen. The player should complete Test Track before Trial by Dirt to avoid this. However, the same time results bug cannot be fixed.