A drop deck trailer is provided with a deck that has the ability to raise and lower to conveniently load and unload goods and materials on the deck. A pneumatic system can raise and lower the deck and also serve as a suspension system for the trailer to dampen the relative movement between a frame and the deck. In addition, some embodiments of the trailer have a deck with a movable carriage that can move along the deck to automatically load a vehicle such as a golf cart. The carriage has rollers that secure the front wheels of a vehicle, and the carriage moves along the decks to pull the vehicle onto the deck. Moreover, various embodiments of a trailer frame can selectively connect to different decks to allow each deck to be specialized for particular goods and materials.