49.24. What are the two main types of coupling devices for freight vehicles?
UAЯкі два основних типи зчіпних пристроїв для вантажних транспортних засобів?
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This exam question from the Traffic Rules of Ukraine concerns the safe operation of cargo vehicles and the correct connection of a vehicle to a trailer link. Understanding the types of coupling devices is important not only for the theoretical exam but also for real-world safety: the type of coupling determines the method of transmitting tractive force, load distribution, the stability of the road train, and the expected behavior during braking and maneuvering.
The question tests knowledge of terms and definitions from the General Provisions section of the traffic rules (point 1.10), which describes what a towing-coupling device is, as well as related concepts such as tractor unit, trailer, and semi-trailer. The logic is simple: one basic type is used for towing a trailer via a drawbar (towing-coupling: tow hitch, hook-loop coupling, etc.), and the other is for working with a semi-trailer, part of whose weight rests on the tractor (fifth-wheel coupling device, known as the "fifth wheel" or "saddle," which locks the kingpin).
The analysis of the options in the test boils down to classification into two main categories, not into individual designs. Combinations like "towing-saddle" or "tow hitch type" as separate types are misleading: "tow hitch type" is actually a variety of towing-coupling, and formulations like "direct drawbar" describe the method of attaching the trailer, not the basic class of device. That is why, in the traffic rules and in the format of theoretical exam tasks, two main types are considered fundamental: towing-coupling for trailers and fifth-wheel (saddle) for semi-trailers.
Clause 1.10 (term “Towing-coupling device”)
Towing-coupling device — a device for connecting a vehicle to a trailer (semi-trailer).
This term in the Traffic Rules defines one of the basic types of coupling devices — towing-coupling (tow bar, hook-loop, etc.), which ensures the towing of a trailer (or, in certain designs, a semi-trailer).
Clause 1.10 (term “Tractor unit”)
Tractor unit — a vehicle designed for towing a semi-trailer and equipped with a fifth-wheel coupling device.
This definition directly indicates the second main type of coupling device for cargo vehicles — the fifth-wheel (so-called “fifth wheel”, “saddle”), which works specifically in tandem with a semi-trailer.
Clause 1.10 (term “Semi-trailer”)
Semi-trailer — a trailer whose axle(s) is (are) located behind the center of mass and which transfers part of its weight to the tractor unit.
This term explains why the fifth-wheel type is used for a semi-trailer: the semi-trailer transfers part of the load to the tractor unit through the fifth-wheel coupling device.
Clause 1.10 (term “Trailer”)
Trailer — a vehicle designed to move in combination with a motor vehicle.
The term “trailer” in the Traffic Rules corresponds to the use of the towing-coupling device as the basic solution for towing trailers.
Thus, the correct answer is “Towing-coupling and fifth-wheel,” considering that according to the definitions in the Traffic Rules, the towing-coupling device is intended for connecting a vehicle with a trailer (semi-trailer), while the tractor unit is directly defined as having a fifth-wheel coupling device for towing a semi-trailer.
In cargo vehicles, coupling devices are classified according to how the trailer link is attached and how the load is transferred between the vehicle and the trailer. In the exam, it is important to distinguish two basic solutions: one is intended for towing a trailer by the drawbar, the other is for working with a semi-trailer, which partially rests on the tractor unit.
The first main type is the towing-coupling device. It is used when a cargo vehicle tows a trailer connected via a drawbar: the force is transmitted to the coupling element of the vehicle (typically a hook/fork/tow bar) and the corresponding element on the trailer (ring/loop). In practice, this is the classic scheme for conventional trailers, as well as for special equipment where the main goal is to reliably transmit the towing force during hauling.
The second main type is the fifth-wheel coupling device. It is used in tractor units for semi-trailers: the semi-trailer is attached via a kingpin, which is locked into the "fifth wheel," and at the same time, part of the semi-trailer's weight is transferred to the tractor unit. This design provides not only a strong connection but also allows the semi-trailer to pivot relative to the tractor during maneuvering.
Other options that are sometimes mentioned (for example, specific types of hook couplings) are essentially variations of one of these two basic types, and not separate "main" categories. Therefore, in the test wording, the general classification is sought.
Thus, the correct answer is "Towing-coupling and fifth-wheel," since the first type is intended for towing trailers via a drawbar, and the second provides coupling of a tractor unit with a semi-trailer with part of its weight transferred to the tractor.