To call Trackmania DS a racing game is doing it a disservice. While it does involve cars on a track, the competition is more against yourself than against any other vehicle in the race.
Race mode is straight forward: get to the finish line as quickly as possible. Race mode is also where players will begin the game because it takes a number of bronze, silver, and gold medals to unlock other modes and tracks in the game. Racing against AI cars felt superficial because there's no actual collision physics, so it's more like racing the clock while having some ghost cars on the track. The opponent's vehicles were helpful while Siliconera was playing a track for the first time because having them in front of them made it easier to see where the track turned next, which is sometimes hard to see on the DS's screen.