Drop Deck Flatbed:
A drop deck flatbed is a platform semi-trailer with no roof, sides and doors, and it has two deck levels. The floor drops down after it clears the tractor unit. The lower deck allows for hauling taller loads than a regular straight floor flatbed.
Drop Decks are also known as Step Decks and Lowboy trailers.
Synonyms:
step deck, step decks, lowboy trailer, lowboy trailers