Truck
Truck, motor vehicle designed
primarily for hauling cargo or for special work or service purposes. Trucks are
usually larger and heavier than automobiles and differ in basic construction.
Most modern automobiles have a unibody construction, in which the body itself
provides structural support for the vehicle. Trucks, by comparison, are built
around a strong metal frame, called a chassis, that supports the rest of the
truck. Trucks usually have larger, more powerful engines and stronger
suspensions than automobiles have. Large trucks have additional axles and
wheels for carrying heavy loads.
Trucks come in many different
varieties and are classified by weight, type, and the job they perform. Light
trucks have a vehicle weight of up to 6,300 kg (14,000 lb) and are used for
light hauling or towing, as well as for everyday transportation. Medium trucks
have a weight of up to 15,000 kg (33,000 lb) and are typically used as dump
trucks, garbage trucks, local freight-delivery trucks, and utility vehicles.
Light and medium trucks are usually powered by gasoline internal-combustion
engines, although some may be powered by diesel engines. Heavy trucks are over
15,000 kg (33,000 lb) in weight and are used primarily to pull trailers. Such
trucks are often called semis (short for semitrailer), or tractor-trailer
trucks, and use large diesel engines for power. Heavy trucks also include large
vehicles designed for off-road work, such as large construction and mining
trucks.
Trucks are also classified
by their construction. Straight trucks have the body, or cab, and cargo
compartment mounted on the same frame. All light trucks and most medium trucks
are straight trucks. In a tractor-trailer truck, the engine and cab are part of
the tractor unit. The trailer is a detachable unit, is separate from the
tractor, and has its own suspension and wheels. It is joined to the tractor by
a hinged platelike mounting device called a fifth wheel.
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LIGHT TRUCKS
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Light trucks include pickup
trucks, minivans and full-size vans, and sport utility vehicles (SUVs). The
engines, transmissions, and brakes of light trucks are usually similar to those
used in passenger cars. Some light trucks offer four-wheel drive for off-road
driving or driving on mud or snow. Light trucks are often used as passenger
cars are for everyday driving, particularly in rural areas, but they also
provide the ability to carry extra cargo when needed. They are used primarily
for light hauling and construction work.
Most pickup trucks have a
cab with two doors and a single bench seat that holds up to three passengers.
Some have extended cabs with a rear seat or additional doors. The cargo area
behind the cab is called the bed. It has raised sides and a fold-down tailgate
at the back for loading and unloading cargo.
Vans are mechanically similar to
pickup trucks, except that the cargo area is enclosed and is part of the body.
Vans typically have side doors and a rear door in addition to the front doors.
A cargo van is equipped with only a front seat, and the unfinished rear area is
reserved for hauling items. Cargo vans are often used to deliver small parcels
and goods in urban areas. A passenger van has multiple seats for carrying extra
passengers, as well as side windows. Some have lengthened bodies to carry up to
15 or more passengers and are used like small buses. A conversion van is a
cargo van that has been specially modified to carry passengers in luxury.
Conversion vans typically have plush interiors, numerous accessories, and
individual seats. Minivans are smaller vans intended primarily for hauling six
to eight passengers. Minivans have mostly replaced station wagons as a family vehicle.
Some minivans have rear-wheel drive, but most have front-wheel drive. They also
have the same engines, transmissions, and suspension components as
front-wheel-drive passenger cars. In addition to the two front doors, most
minivans have one or two sliding side doors and a rear liftgate that opens
vertically.
Many light trucks are
adapted for special uses. Tow trucks have a derrick and winch for towing
vehicles, or a tilting bed for carrying disabled vehicles. Many ambulances are
also built on light-truck frames. Large police trucks, nicknamed paddy wagons,
have an enclosed confinement area in the back for transporting groups of people
who have been arrested. Some police departments in large cities also have
specially armored trucks for use by riot teams or bomb disposal units.
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MEDIUM TRUCKS
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Dump Truck
Dump trucks have large open beds for
hauling loose material such as gravel or soil. To empty the bed's contents, a
hydraulic lift inside the truck tilts the bed, dumping the contents behind the
truck. Dump trucks are common at busy construction sites, where large amounts
of building materials are frequently moved.
Medium-duty trucks have larger
engines and frames than do light trucks and often have dual rear wheels or a
second rear axle for carrying additional weight. Medium trucks are used
primarily for local delivery work, for construction, and by municipal and
utility fleets. Dump trucks have a hydraulically powered bed that tilts up and
down for hauling and dumping rock, gravel, dirt, and debris. Garbage trucks
have a large enclosed compartment and a hydraulic compressor for compacting and
hauling refuse. Utility trucks with a boom and basket, nicknamed cherry
pickers, are used by utility companies for lifting people up to work on utility
lines or trees. Fire engines often have a large internal water tank and pump
for fighting fires. Some carry large ladders for reaching the upper floors on
multistory buildings. See Fire Fighting.
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HEAVY TRUCKS
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Tractor-trailer Truck
Tractor-trailer trucks, also called
semis, haul much of the freight in the United States and a significant
percentage of freight in the rest of the world. Trailers can deliver raw
materials, refrigerated goods, and finished products to factories, warehouses,
and markets. The tractor shown here includes a sleeping compartment so the
driver can rest during long trips.
Heavy trucks have the
largest frames and are usually powered by large diesel engines. They have
multispeed transmissions, with as many as 18 gears, for pulling heavy loads.
Most semis or tractor-trailer trucks have two rear drive axles, called dual
tandems, each of which has dual tires on each side. Trucks with this
arrangement are nicknamed 18-wheelers because of the total number of wheels
under the truck and trailer.
When a heavy truck is
assembled, the type of engine, transmission, brakes, axle arrangement, and
other equipment used are usually specified by the individual or company that is
ordering the truck. Almost all heavy trucks have power steering, cruise
control, and air brakes. Air brakes use compressed air, rather than brake
fluid, to activate and release the brakes. An air reservoir in the truck
supplies air to the brakes through air hoses. The constant supply of air keeps
the brakes released. Pressing on the brake pedal decreases the air pressure and
applies the brake. If the brake system malfunctions or if the air hoses become
punctured, the brakes apply themselves automatically as a safety precaution.
Most heavy trucks are
designed for hauling goods over long distances, known as over-the-road hauling,
although some are also used for local deliveries. The truck cab may be
positioned behind the engine and hood or located directly over the engine. The
latter is called a cab-over design, and it reduces the overall length of the
truck-trailer combination. Cab-over trucks are hinged to tilt forward when
engine access is necessary for maintenance or repairs. Most long-haul heavy
trucks have a sleeper compartment, behind the cab, that contains a bed for the
driver. The sleeper compartment is the truck driver’s home away from home and
may be equipped with a television, a microwave oven, and a refrigerator. Most
heavy trucks are also equipped with citizens band radio for communication. Some
truck fleets use satellite tracking equipment to monitor their trucks, so the
fleet operator or dispatcher can know a truck’s location at any time.
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TRAILERS
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The large trailers pulled
by semi tractors have their own rear suspension and wheels, with the front of
the trailer being supported by the fifth wheel on the tractor. Semi trailers
also have folding supports under the front that are lowered when the trailer is
detached from the tractor and parked. The brakes on the trailer’s axles have
air hoses that attach to the tractor’s brake system, so the tractor and trailer
brakes work together. Trailers have their own signal, tail, and brake lights,
all of which are powered by the tractor’s electrical system.
Trailers come in many
different designs, depending on the intended cargo. Enclosed, or standard
box-type trailers are used to haul a wide variety of goods and merchandise.
Double trailers are often used on roads that have sharp turns. Double trailers
resemble two smaller trailers linked together and can maneuver through tight
turns more easily than standard trailers can. Size and weight restrictions
apply and vary from state to state. In the United States, tractor and single
trailer combinations generally must be less than 16 m (53 ft) in length and are
limited to a maximum weight of 36,000 kg (80,000 lb). Separate weight limits
apply to trailers with single or tandem axles and to double trailers. Maximum
trailer height and width are dictated by state law and vary from state to
state. For most states, the maximum height is 4.11 m (13.5 ft), and the maximum
width is 2.6 m (8.5 ft). In some states, trailers may be equipped with
additional wheels and axles to carry heavier loads.
A special type of enclosed
trailer is an insulated and refrigerated “refer” unit, used for transporting
perishable food items. Refrigerated trailers have a small engine mounted on the
trailer for powering the refrigeration system. This allows the refrigeration
unit to run continuously, even when the trailer is parked or disconnected from
the tractor.
Piggyback trailers are enclosed
trailers designed to be mounted on railroad flatcars for cross-country
transport. Some have their own wheels and suspension, while others are sealed
containers that are lifted off and placed on a trailer chassis. Sealed
containers are also used on special ships, called container ships, to transport
goods overseas.
Flatbed trailers are used
to transport large objects such as construction equipment, industrial
machinery, and oversized objects. Such trucks may be equipped with an Oversize
Load warning sign and flashing lights, and may be accompanied by an escort vehicle
to warn other motorists.
Platform trailers are
essentially large containers with open tops for transporting produce and grain.
Special trailers are also designed for hauling livestock, automobiles, and
beverages.
Tank trailers, known as
tankers, are used to haul chemicals, milk, gasoline, and other liquids.
Tankers, as well as other trucks that carry flammable or toxic products, must
display special warning emblems to warn police and firefighters in case of an
accident.
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TRUCKING OPERATIONS AND REGULATIONS
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Trucking has become the
predominant means of delivering all types of goods, accounting for four-fifths
of all domestic freight value in the United States. Trucks in the late 1990s
hauled 1.5 trillion ton-kilometers of freight annually (a ton-kilometer is the
movement of one metric ton over the distance of one kilometer). All types of
manufacturing are also dependent on trucking for deliveries of parts and for
shipping finished goods.
A trucking trade association
estimates that about 9.7 million people in the United States are employed in
trucking industry jobs, a figure that includes about 3.1 million professional
truck drivers. In 2002 there were about 588,000 trucking companies in the
United States. They generated over $580 billion in gross revenues.
At the beginning of the
21st century there were about 87.1 million trucks of all types on U.S.
highways, out of a total of 217.6 million vehicles. The majority of trucks on
the road were light trucks such as pickups and sport utility vehicles (SUVs);
only about 21.3 million were trailers and semitrailers. In Canada, about
450,000 trucks are used to carry commercial freight.
Trucks that operate between
states must be licensed in each state through which they travel, and their owners
must pay road fees in each state. Trucks may be licensed to over-the-road
commercial carriers, private delivery companies that operate their own trucks,
or private owner-operators. Trailers are licensed separately from tractors and
may be owned separately by a different company or fleet. There are about 4.7
million commercial semitrailers in the United States.
Drivers of over-the-road trucks
must have a commercial driver’s license, which is obtained by special training
and the passing of written and driving examinations. Drivers must also keep
written logbooks of their hours and miles traveled, as these are regulated for
safety purposes to minimize driver fatigue. Drivers who work for trucking
companies are generally paid by the mile, while owner-operators and commercial
carriers charge for freight by weight and distance. A typical commercial
over-the-road truck is driven over 161,000 km (100,000 mi) a year.
Trucking operations are
regulated by state and local agencies to ensure safety on the road. Trucks
traveling on interstate highways and primary roads must be inspected at weigh
stations to make sure they are not overloaded. Drivers are fined if the weight
exceeds the limit allowed for each axle. Trucks are also subject to safety
inspections and may be put out of service if the brakes, tires, or other safety
equipment do not meet standards. Because big trucks are so large and heavy,
they cannot stop or maneuver as quickly as cars and light trucks can. Of the
almost 42,400 traffic fatalities that occurred in the United States in 2000,
about 12 percent involved heavy trucks. In most car-truck accidents, the truck
driver often is uninjured or suffers only minor injuries because of the size
difference between the vehicles.
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HISTORY
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Various steam-powered carriages and
vehicles were built in Europe from 1769 through the late 1800s. However, one of
the first gasoline-powered vehicles for hauling cargo was built in 1896 by
Gottlieb Daimler in Germany. The earliest trucks were essentially self-powered
wagons, most of which had an open driver compartment in the front. In 1898 the
Winton Company of Cleveland, Ohio, became one of the first manufacturers of
trucks in the United States. In 1903 the first truck show in the United States
was held in New York City. In 1911 the first transcontinental coast-to-coast
trip by a truck was completed in 66 days.
In the early 1900s trucks
were used primarily for local deliveries and limited intercity commerce. Roads
were poor, and railroads controlled the long-distance shipping of freight. As
roads improved and more highways were built, however, the role of trucking in
commerce grew in importance. The Federal-Aid Road Act of 1916 promoted the
building of paved roads between cities to facilitate travel and commerce. By
the end of World War I (1914-1918), more than 600,000 trucks were in use in the
United States. Trucks proved to be an invaluable method for moving both
soldiers and supplies during the war, and were also used extensively as
ambulances for transporting wounded soldiers.
In 1935 the Congress of
the United States passed the Motor Carrier Act to expand the role of the
Interstate Commerce Commission (ICC), a federal agency that regulated commerce
between the states. The ICC was originally created to regulate commercial rail
and water transportation. Its new authority allowed the ICC to establish
regulations for trucking companies involved in interstate business.
As the nation’s highway
system expanded, so did the use of trucking to move goods and produce. The
construction of the interstate highway system in the late 1950s and 1960s made
long-haul trucking not only practical but also highly competitive with rail
freight. In 1980 the trucking industry was deregulated, allowing the
establishment of many small independent trucking companies. Deregulation
stimulated competition in the trucking industry and generally lowered the cost
of shipping freight by truck.
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