Successfully complete each of the four parking levels to unlock an additional parking level. Successfully complete the bonus parking level to unlock a sixth parking level.
Complete arcade mode with all four characters to unlock two bonus trailers in score attack mode, versus mode, and arcade mode (if the Nippon Maru is selected).
To unlock two extra parking stages, finish all the original parking levels.
Complete Arcade mode with all four original truckers to unlock Nippon Maru, a brand new trucker.
Once you have Nippon maru, when you play Attack, Vs, or Arcade you will have two new trucks to choose from.
Go into the options menu, select "Difficulty" and set it to "Very Easy". Next, save the game in the options menu and return to the main menu. Select arcade mode and you will have more time in each level, until you reach into the last level and complete the game.
Successfully complete arcade mode with all four characters