18 Wheeler
Bonus Parking Levels
Complete each of the four parking levels to unlock a bonus parking level. Completing this bonus level will unlock a further bonus parking level.
Drive Nippon Maru
Hold X and press Start at the title screen. Keep X held until the mode selection screen appears. Choose any mode to drive the Nippon Maru truck. Completing arcade mode with all four trucks also unlocks this feature.
Submitted by LiquidFox.
Lizard Tail
Complete arcade mode with the four trucks, and the bonus fifth truck (Nippon Maru) to unlock the Lizard Tail.
Submitted by LiquidFox.
The database at Game Oak contains more information regarding 18 Wheeler for Sony PlayStation 2.