The term "motorcycle trailer" most commonly refers to a wheeled unit that securely tows a motorcycle; the unit is towed by an automobile. The term may also refer to a trailer affixed to the back of a motorcycle that can allow the motorcycle to haul cargo. A motorcycle trailer that is meant to haul a motorcycle behind an automobile must be street legal; this means it must feature brake lights, meet size regulations, meet tire and axle regulations, and be properly designed for handling different road conditions. A motorcycle trailer meant for attachment to a motorcycle must usually also be street legal, though some trailers do not necessarily need to be.
Countless motorcycle trailer designs exist to suit different purposes. A one-motorcycle trailer, for example, might feature two wheels and a narrow deck on which the motorcycle can be secured, and the deck may feature a hinged gate that makes wheeling the motorcycle onto the deck much easer. The gate also adds extra security by providing a barrier in the rear of the trailer should the motorcycle work loose during transport. Other styles of trailer may raise and lower using a hydraulic lift; the motorcycle can be driven onto the trailer, which can then be raised off the ground for transport. Such a design is often used on the back of RVs, and the unit itself must be properly mounted to the frame of the RV or automobile.
Some motorcycle trailer varieties are made to accommodate more than one motorcycle. These trailers are often much larger and heavier than smaller motorcycle trailers, so a full-sized truck or medium-sized truck or SUV is often required to tow such a trailer. Multi-purpose trailers can also be used to haul a motorcycle, though the user will have to find a way to properly secure the motorcycle during transport. Another variety of trailer is the enclosed trailer, which is similar to other types of motorcycle trailers in build and specification, but instead of exposing the motorcycle to the elements during transport, an enclosed trailer covers the motorcycles. The enclosure is often made of wood and sheet metal, or some other durable surface that is resistant to rust and corrosion from the elements.
Trailers that are hauled behind motorcycles are much smaller units often used for stowing luggage or other cargo. These, too, must be street legal if they are to be used on the road; this means they must feature brake lights and they must meet size and construction requirements. They are useful for long tours or trips, and they often feature locks and other security measures to ensure the safety of the cargo being hauled.