Typically, this length comes from the semi-truck's frame, or the extended steel section towards the truck's rear that supports the majority of the wheels and cargo.

There's a good reason why most of the semi-trucks on the road are rear-wheel drive. The alternative doesn't make much sense once you consider usage.

The semi truck rumbled down the congested, ... In the back seat of the truck’s sun-drenched cabin, ... Section A, Page 1 of the New ...

Typically, this length comes from the semi-truck's frame, or the extended steel section towards the truck's rear that supports the majority of the wheels and cargo.