|Rocky Mountain Double:|
There are both "semi-trailers" and "full trailers" (also simply called "trailers"). When a semi-trailer is attached to the tractor, part of its weight rests on the tractor. Not so with a full trailer. No part of a full trailer rests on the tractor.
The federal height limit for trailers is 13 feet, 6 inches measured from the highest point on the tractor or trailer to the ground or road surface. Some western states allow heights of up to 14 feet. However, some cities such as New York, Chicago, and Boston have restrictions, so not every trailer can go everywhere in the country.
Types of Trailers:
The Dry Freight Trailer
This is the plain enclosed box on wheels. Dry freight Trailers haul appliances, clothing, furniture, and other items. Whatever is hauled in a dry freight van, it won't be anything that must be maintained in a particular temperature range.
The Insulated Trailer
When goods need more protection from cold weather during shipment, they are hauled in an insulated trailer. An insulated trailer is simply a dry freight trailer with insulated walls and ceiling. The insulation helps maintain a certain temperature range without further refrigeration.
The Refrigerated Trailer
A refrigerated trailer is often referred to as a "reefer". A reefer has a refrigeration unit and has insulation in the walls, floor, and ceiling to maintain precise temperature. The trailer has a refrigeration unit mounted on it. These trailers are used to haul food and other perishable items.