In Time Trial, the player competes as a single playable character on the race track without any teammates to race with or rivals to race against. The Event has no lap limit or Item Boxes lying around on the race track, and is used purely to test the player's skills.
During a Time Trial Event, the player's objective is to complete a single lap around the chosen race track as fast as possible. When starting out a lap, the player will be equipped with three White Wisps to use the White Boost with while a timer in the upper left corner of the screen starts measuring the time the player takes to complete a lap. Once the lap around the race track has been completed, the player will be equipped with three new White Wisps (if they have not used them up already) and the timer will reset, thus starting the lap race all over. However, the player's best time will be saved for future reference. Before starting a Time Trial though, the player can choose between two modes for it:
Personal Best: A basic single-player race where the player around on the race track, trying to complete a lap in the shortest time possible.
Ghost Level: A basic single-player race where the player around on the race track, trying to complete a lap in the shortest time possible. However, the player will be contenting with the "ghost" of a player - an intangible image of a racer car who is replaying its fastest playthrough through the lap. In addition, the player is given a listing of the best lap times for a track on the left side of the HUD. These listings can list up to the four best lap times, with the four-best time having a bronze medal assigned to it, the third-best time having a silver medal assigned to it, the second-best time having a silver medal assigned to it, and the best time having a platinum medal assigned to it. If the player can beat any of these times, they will be awarded with the appropriate medal(s) (beating the bronze-leveled time, but not the silver-leveled time, for example, will reward the player with a bronze medal).
A Time Trial Event has no way of being completed; it will just keep repeating itself every time the player completes a lap. As such, the only way to end it is by going to the menu and aborting the Time Trial manually.