Semi-trailer truck

A Tractor is a trailer of a tractor (also semi truck called ), which usually is technically based on a truck chassis, and a semi-trailer (also semi-trailer, semi-trailer, bridge, semi-trailer or trailer called ), is mentioned in the official language articulated vehicle. The term tractor is just slang for such vehicles in Germany, in Austria, it is the legal term for the combination of tractor and semi-trailer. In an articulated vehicle so it is a fifth wheel (also saddle plate also) is threaded to attach the trailer to the combination of a short truck tractor with cab, steering and drive axle (s), engine and transmission, on the short frame.

  • 2.1 Germany
  • 2.2 Sweden
  • 2.3 USA
  • 2.4 Canada
  • 2.5 Mexico
  • 3.1 Advantages
  • 3.2 disadvantages



The tractor is a derived from normal truck vehicle having a fifth wheel instead of a truck bed. This fifth wheel consists of a plate with built-in locking mechanism, which rests on the trailer and into the kingpin of the trailer is coupled. Thus, the trailer with the tractor unit is movably connected but surely. A tractor unit normally has a shorter chassis than a comparable truck tractor unit have no truck bed and thus represent a special form of the truck, which is considered the tractor as traffic rules and EU law. All major truck manufacturers have tractor unit on offer.

For the purpose of carriage of goods tractor and semitrailer are always needed. The semi-trailer, similar to the trailer, is powered by the tractor unit with the necessary compressed air for the braking system and the electrical power for the vehicle lighting, ABS and so on.

For driving with articulated vehicles ( solo) is a driver's license with Class B (for towing up to 3.5 tonnes gross vehicle weight), C1 (for towing up to 7.5 tonnes gross vehicle weight) or C (for towing vehicles weighing more than 7.5 tonnes gross vehicle weight ) is necessary. To drive a semi-trailer exceeding 750 kg the towing vehicle according to the respective trailer driving license BE/C1E/CE is additionally necessary.


The semi-trailer is a kind of long "trailer", which, however, one has no front axle and four rear axles, front and usually additional herabkurbelbare supports for coupling and uncoupling. The rear axle of the tractor replaced virtually the front axle of the semitrailer. The tractor is built very short, so the trailer may be longer.

In a special semi-trailer, which must carry a greater weight, even more axes may be present. Individual axes can be designed as lift axles during triaxial semitrailer, which can be raised when running empty to minimize the interleaving of the wheels and tire wear ( " erasing" ) when cornering and rolling resistance and therefore fuel consumption (eg empty or light load ) to reduce. The air brake lines are similarly connected to a truck - trailer towing vehicle through two hose lines, a third line connecting the lighting system of the trailer with the tractor ( tractor unit ). The load of the semi-trailer is in part on the rear part of the three axes, a major part of the tractor carrying the fifth-wheel coupling. This has an advantageous effect on the traction of the tractor.

When uncoupling the trailer is placed on two saddle supports, which are rolled down. You can adjust these supports with a crank via a transmission and a spindle in height. A power- saving option is to lower down after cranking the supports the tractor vehicle with air suspension and then go away under the semitrailer. The design of the loading area is dependent on the intended use, there are countless variations, from the trailer with tipping over curtain canvas semitrailer to the container chassis.


Since it is not as maneuverable with tractor-trailers as a normal truck, these are mainly used in long-distance freight transport, especially by their possible total weight of up to 44 tonnes in combined transport ISO containers. In normal traffic t total weight is only 40 admitted. In European intercity usually two-axle tractors are used with three-axle trailers ( it 's a common one lift axle ). But even as a construction vehicle with dump body meets one articulated vehicles more and more often.

For large-volume transport of goods with lower payload special semi-trailer to be built. These so-called mega- liner or jumbo trailers have wheels with a smaller diameter. This increases the internal loading height at a constant total height. Alternatively, a second loading level are drawn ( biplane with 25 % more capacity for pallets). However, the smaller wheels are a disadvantage in handling and the tires are worn more quickly. In this case, both the towing vehicle and the trailer have smaller wheels. But there is also an intermediate solution in which the towing vehicle has a full-size tires and the trailer has a step in the loading area. Due to its shape it is then known colloquially as gooseneck trailers (English: Gooseneck chassis) respectively. Semi some additionally also have a built-in lifting stage, so that the trailer can be loaded from the rear normal.


In six states are currently being tentatively called the Euro Combi (often incorrectly referred to as GigaLiner what is actually the name of a structure - producers ) were used. These are two different types:

  • (Type A): a three-axle trucks ( with solid construction or swap body ) with attached dolly on which a semi-trailer is out.
  • (Type B): a tractor with three-axle semi-trailer and a tandem trailer with a tandem axle

These oversized or long - Euro Combis could be operated until the end of 2007, only with a special permit in Germany. The total length must not exceed 25.25 m instead of the usual 16.50 m 18.75 m when the tractor or truck. The exemption did not extend to the total weight, which remains at 40 t, but should be under certain circumstances up to 60 t extended. Currently, a report by the Federal Highway Research Institute is awaited and the policy must then decide for pro or contra.


In Sweden, the total weight can be up to 60 t.


In the U.S. the Department of Transportation (DOT) has determined to supportive dimensions of tractor trailers (semi- trailer trucks) for the nationwide traffic on the Interstate highway system. Here are 102 inches wide (2.59 m), 13 feet 6 inches in height ( 4,115 m) and a maximum of 80,000 pounds gross vehicle weight ( 36.3 t). These measurements are extended by some states, especially in many places road trains with multiple trailers allowed - a " Turnpike Double" bonds two 48 -foot trailers ( 14.6 m ) to a train with a permissible total weight of 147,000 pounds (66, 7 t), the "Rocky Mountain Double" combines a 40-foot semi-trailers ( 12.2 m) with a 28- foot-6 -inch pendant ( 8.7 m) ( the " Pup " ) with a team up to 129,000 pounds ( 58.5 t) the total weight.


In Canada, the limits are higher than in the U.S., depending on the configuration, a maximum of 137,500 pounds ( 62.3 t) gross weight, maximum 53 -foot semi-trailers ( 16.2 m) and a total length ( of the road trains ) up to 75 feet 6 inches ( 23.0 m) allowed.


In Mexico, for some configurations of up to 136,000 pounds ( 61.7 t) the total weight up to 68.2 feet ( 20.8 m) overall length for articulated vehicles with a trailer and up to 102.7 feet ( 31.3 m) overall length allows for articulated trucks with two trailers. The high gross weights over 60 tonnes tight regulations on axle loads, the number and minimum distances of the axes have produced in order to limit the burden of bridges (so-called " bridge formula" / bridge formulas of the axis configuration).

Advantages and disadvantages of commercial vehicles


  • Flexible Replace the trailer in a company to comply with travel times
  • The semi-trailer may have a very long, up to the frame - buckling far mostly flat, continuous cargo space, which can be build relatively inexpensive.
  • Unproblematic loading and transporting long goods (such as steel beams )
  • Transport of goods, which require a relatively small space, but have a high weight is very possible.
  • Flexible system of many cheaper semi-trailers with a few (expensive) articulated lorries
  • Simpler (backward ) maneuvering with less complex motion mechanics as comparatively the truck with trailer
  • Lower curb weight compared to articulated trains with the same GVW
  • The tractor -trailer without tractor is considered. Tractors are exempt from the Sunday and holiday driving bans that apply in some European countries for trucks, allowing the driver to remain mobile even on Sundays and holidays, and the forwarder to dispose its fleet also ban days.
  • It's just a ramp touch the complete loading and unloading required ( time saving).
  • The frequent disconnection or connection of trailer and towing vehicle, particularly when loading and unloading is eliminated.
  • Better handling, because the trailer rare or hardly begins to lurch.
  • Lower fuel consumption, since the distance between the tractor and trailer is very low and therefore caused less turbulence than in articulated. Even better driving characteristics lead to lower consumption, which accounts for a total of 3-5%.


  • A tractor itself is useless without semi-trailer, a truck alone, however, can also transport goods without trailer.
  • Partly problematic driving behavior of truck tractor when driving without semi-trailer
  • Crosswind hazards empty, large-scale semi-trailer
  • Higher tire wear especially on trailers without steered axles
  • Dangerous winter driving behavior, as in the usual Zweiachssattelzugmaschine the drive axle of the truck is ( the tow point of the trailer ) behind the fifth wheel and king pin. On slippery, wet roads, the rear axle of the tractor therefore tends to break the side and trying to overtake its own fifth wheel.
  • The axle load (especially the drive axle of the tractor ) is the Euro - Tractor to three tons higher than in the euro - articulated, leading to increased wear of roads ( ruts ), which is why the utilization of such a vehicle using the defined in the EEA Member States nationally specified maximum axle loads is not always possible and can cost up to three tons of payload.
  • Problems in hairpins and narrow driveways
  • Swinging when cornering in the front and rear of the trailer can endanger other road users
  • Different axle tire wear (only for semi-trailers with more than two axles )