How is a truck tractor defined?

A truck tractor is defined as a vehicle specifically designed to draw another vehicle while not necessarily carrying a load itself. This means that its primary function is to provide the motive power to another vehicle, typically a trailer or semi-trailer, which is where the cargo or payload is contained.

This definition is key in understanding the difference between various types of vehicles. While a truck tractor may be associated with heavy-duty applications, its primary characteristic is its role as a towing vehicle, not as a payload carrier. Thus, its design focuses on power and the ability to connect and transport other vehicles rather than carrying freight itself.

In contrast, the other options describe different kinds of vehicles or their uses, but they do not accurately reflect the specific function and definition of a truck tractor.