truck

truck, any motor vehicle designed to carry freight or goods or to perform special services such as fire fighting. The truck was derived from horse-driven wagon technology, and some of the pioneer manufacturers came from the wagon business. Because of a well-developed system of roads and highways in North America and Europe, trucks have come to carry most intercity freight, with the exception of bulk materials such as ores, which are typically still carried by ship and rail, and time-critical deliveries, which are usually carried between cities by air. Trucks enjoy an almost total monopoly in intracity freight delivery because of their ability to deliver goods directly to recipients.

In 1896 Gottlieb Daimler of Germany built the first motor truck. It was equipped with a four-horsepower engine and a belt drive with two speeds forward and one in reverse. In 1898 the Winton Company of the United States produced a gasoline-powered delivery wagon with a single-cylinder six-horsepower engine.

In World War I motor trucks were widely used, and in World War II they largely replaced horse-drawn equipment. A notable vehicle was the four-wheel-drive, quarter-ton-capacity, short-wheelbase jeep, capable of performing a variety of military tasks.

In the last quarter of the 20th century, new truck sales grew tremendously in the United States. In large part, this happened because of the introduction of utility and sport utility vehicles, which are classified as light trucks but operated as family vehicles. Light trucks accounted for more than 90 percent of all truck sales and roughly half of total vehicle sales in the United States annually by the start of the 21st century. This phenomenon was unique to the American market; worldwide, trucks are purchased mainly for commercial operation.

Types and definitions

Trucks can be classified as either straight or articulated. A straight truck is one in which all axles are attached to a single frame. An articulated vehicle is one that consists of two or more separate frames connected by suitable couplings. A truck tractor is a motor vehicle designed primarily for drawing truck trailers and constructed to carry part of the weight and load of a semitrailer, which is a truck trailer equipped with one or more axles and constructed so that the end and a substantial part of its own weight and that of its load rests upon a truck tractor. In contrast, a full trailer is constructed so that all of its own weight and that of its load rests upon its own wheels.

A device called a fifth wheel is used to connect a truck tractor to a semitrailer and to permit articulation between the units. It generally includes a lower half, consisting of a trunnion (pivot assembly) plate and latching mechanism, mounted on the truck tractor for connection with a kingpin mounted on the semitrailer. A semitrailer may be converted to a full trailer by a trailer-converter dolly, an auxiliary axle assembly equipped with the lower half of a fifth wheel, a drawbar, and other special parts.

Axle assemblies of heavy trucks may be made up of two or more axles, any of which may be powered. Normally, they are spaced so that the distance between axle centres is not more than one and one-half times the overall diameter of the wheel and tire. If the axles are separated by a larger distance, the assembly is called a spread tandem.

Trucks are organized for regulatory purposes in the United States by their fully loaded capacity, or gross vehicle weight (GVW) rating. Light trucks have GVW ratings that do not exceed 10,000 pounds (4.5 metric tons); GVWs of less than 8,500 pounds (3.9 metric tons) are classified as work trucks. These vehicles generally have more in common with passenger cars than with larger trucks. More than half of the world production of trucks consists of light pickup trucks, utility vehicles, and vans. Medium trucks have GVW ratings of 10,000 to 26,000 pounds (4.5 to 11.8 metric tons) and are generally straight designs. They make up about 3 percent of sales. Heavy-duty haulers with GVW ratings of more than 26,000 pounds are cross-country tractor-trailer combinations and off-road construction or mining trucks; these account for the remainder. A small number of off-road vehicles have GVW ratings that exceed 80,000 pounds (36.3 metric tons). About 15 million trucks are added to the world total each year, but since 2004 the ratio of trucks to passenger cars in the world has decreased annually.

Truck operators are taxed and regulated by government agencies. Approximately half of the revenues that are collected from federal and state highway users in the United States come from the trucking industry. Regulations limit the permissible length, height, weight, safety standards, speed, and noise and exhaust emission levels. Standards are generally similar to those for passenger cars.

Between 150,000 and 400,000 recreational vehicles (RVs) are produced each year in the United States, depending on economic conditions. These are primarily vans and panel trucks that are modified by RV manufacturers. Half of the units are trailers that are not self-propelled. The majority of these are attached to cars and trucks by a ball-type hitch. A portion, however, are towed by light trucks with fifth-wheel hitches mounted on the truck bed. This arrangement permits greater loading on the hitch. Motor homes built on truck chassis that have been supplied by major truck manufacturers to the builders account for the balance of recreational vehicle production.

Truck aerodynamics is important for efficient high-speed highway transportation. Cab designs include extended surfaces that smooth the flow of air over and around the truck and trailer bodies and baffle air flow under the truck to reduce drag and lower the cost of truck operation. Narrowing the space between the truck cab and the trailer has a similar effect. Total operating cost savings of 22 percent have been projected for improved truck aerodynamics.