Extra parking level
Beat the first 4 levels to unlock truckstop.
New Truck And Trailer
Beat very easy mode with all the truck and there should be a tight truck with lights and 2 trailers.
Extra Parking Levels
When you beat the last parking level, there will be 2 tracks, truckstop and factory.
Extra truck
Beat game once in arcade mode and a chinese cabover truck will appear in the truck selection menu.
Nippon Maru
Successfully complete arcade mode with all four characters.
Bonus trailers
Successfully complete arcade mode with all four characters to unlock two bonus trailers in score attack mode.
Lizard Trail
Successfully complete the game with all five trucks (Asphalt Cowboy, Stream Line, Long Horn, Highway Cat, and Nippon Maru).
More Time
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.