Legal definition
Automobile designed and built mainly to tow a semi-trailer.
RDL 6/2015, Annex I, point 23 (translation)Definition
A tractor unit is an automobile designed and built mainly to tow a semi-trailer. Coupled to a semi-trailer, it forms an articulated vehicle.
Tractor unit, articulated vehicle and road train
Three words for three different things. The tractor unit is the motor vehicle alone. An articulated vehicle is that tractor unit with a semi-trailer coupled to it. A road train (tren de carretera) is a motor vehicle with a full trailer hitched instead. Neither the tractor unit nor the road train belongs to the special-vehicle group — an agricultural tractor does. Their speed limit is 90 km/h on motorways and dual carriageways and 80 km/h on conventional roads.
Key facts
- The tractive unit: it hauls the semi-trailer rather than carrying the load.
- Tractor unit + semi-trailer = articulated vehicle, treated as a combination of vehicles.
- With a full trailer instead, the combination is a road train.
- Not a special vehicle; 90 km/h on motorways, 80 km/h on conventional roads.
Frequently asked questions
- What is a tractocamión?
- The motor vehicle designed and built mainly to haul a semi-trailer — the tractor unit. It does not carry the load itself.
- What is the difference between a tractor unit and an articulated vehicle?
- The tractor unit is the motor vehicle alone; the articulated vehicle is that unit with a semi-trailer coupled to it.
Practice real questions on this topic
Free DGT 2026 test with exam-style questions and explanations. No signup. Or explore the free DGT test in English hub for everything in one place.
In the DGT exam
- Which behaviour increases crash risk when driving a lorry, even without exceeding the permitted maximum speed?
- The truck you are driving is 2 metres wide. What lights must it carry due to its width?
- The C1 licence authorizes automobiles whose MAM: