While traveling throughout the entire country, you might have noticed that in different regions of the United States the locals may call their trucks as a tractor, tractor-trailer, big-rig, semi-truck, or 18-wheeler.
And you might ask yourself where from does this words come from? Is a trailer truck and a tractor the same thing?
All these trucking industry related words may mean different things in different regions and dialects, which confuses you as a truck driver.
If you still wonder what is the difference between a tractor-trailer and a truck, or why is heavy-duty vehicle given these weird names, I’ll try to bring some light into the meaning of this trucking industry lingo below.
Truck vs tractor-trailer
What is a tractor?
Did you know that the tractor was invented to replace animals being used as a power force in agricultural activities?
A tractor is a vehicle mainly used for agricultural purposes such as planting, fertilizing, plowing, cultivating, or pulling big and heavy loads. Its body features a powerful engine, gearbox, steering system, brakes, and a seat for the driver, which allows it to provide motive force at a low speed. And while the tractor’s speed is enough to satisfy the agricultural needs it is not enough to carry cargo on a highway.
So if you have heard the saying – “any vehicle producing traction is technically a tractor”, it's important to understand that when we talk about a tractor as a type of truck, we mean trucks designed specifically to pull trailers on a highway.
What is a truck?
A truck is a tractor engine unit with wheels. Essentially, it is a semi-truck.
It doesn’t have a trailer attached .
A semi-truck differs from other types of truck configuration by having a fifth wheel mounted over the rear axle that enables it to attach and pull a trailer.
What is a semi-trailer?
A trailer that relates to a long-haul tractor is called a semi-trailer and it has 8 wheels.
It’s called like that because it doesn’t have the front axle.
While the trailer is not attached to a tractor, its front side is supported by its landing gear.
Also, the semi-trailer doesn’t have an engine. To be moved, it needs to be attached to a tractor unit. In case the tractor has an issue, it can be replaced with another tractor to pull the trailer. It can simply be hooked to the fifth wheel which is located on the tractor’s steer axle and moved.
What is a tractor trailer combination?
A tractor-trailer is the combination of a heavy-duty truck and a semi-trailer where the trailer is attached to the tractor’s fifth-wheel.
Such a tractor-trailer may carry up 80,000 pounds of freight legally.
This type of truck is often referred to as an 18-wheeler (10 wheels on the tractor + 8 wheels on the trailer), semi-trailer truck, tractor-trailer, articulated truck, artic, big-rig, articulated lorry.