facilities and storage of building materials during construction projects. The trailers are equipped with radios for communication. Travel Popular campers use lightweight trailers, aerodynamic trailers that can be towed by a small car, such as the BMW Air Camper. They are built to be lower than the tow vehicle, minimizing drag. Others range from two-axle campers that can be pulled by most mid-sized pickups to trailers that are as long as the host country's law allows for drivers without special permits. Larger campers tend to be fully integrated recreational vehicles, which often are used to tow single-axle dolly trailers to allow the users to bring small cars on their travels. Teardrop Semi A semi-trailer is a trailer without a front axle. A large proportion of its weight is supported either by a road tractor or by a detachable front axle assembly known as a dolly. A semi-trailer is normally equipped with legs, called "landing gear", which can be lowered to support it when it is uncoupled. In the United States, a single trailer cannot exceed a length of on interstate highways (unless a special permit is granted), although it is possible to link two smaller trailers together to a maximum length of . Semi-trailers vary considerably in design, ranging from open-topped grain haulers through Tautliners to normal-looking but refrigerated x enclosures ("reefers"). Many semi-trailers are part of semi-trailer trucks. Other types of semi-trailers include dry vans, flatbeds and chassis. Many commercial organizations choose to rent or lease semi-trailer equipment rather than own their own semi-trailers, to free up capital and to keep trailer debt from appearing on their balance sheet. Full A full trailer is a term used in the United States and New Zealand for a freight trailer supported by front and rear axles and pulled by a drawbar. In Europe this is known as an A-frame drawbar trailer, and in Australia it is known as a dog trailer. Commercial freight trailers are produced to length and width specifications defined by the country of operation. In America this is wide and long. In New Zealand, the maximum width is while the maximum length is , giving a 22-pallet capacity. As per AIS 053, full trailer is a towed vehicle having at least two axles, and equipped with a towing device which can move vertically in relation to the trailer and controls the direction of the front axle(s), but which