What is a Bobtail?

What is a “bobtail” or a bobtail truck?

In trucking slang, bobtail, bobtail truck, and bobtailing refers to a semi-truck without an attached trailer.

Additionally, the Department of Energy calls a straight truck transporting propane gas a bobtail.

Typically, most truck drivers do not like to bobtail. Besides not generating revenue while bobtailing, trucks can become more difficult to drive. Trucks are designed to carry heavy trailers, so when there is none, drivers must be more careful while maneuvering and braking. Despite weighing less, bobtail trucks require a longer braking distance. They are more susceptible to skidding out on tight curves and turns, even with anti-lock brakes. 

Origin of the slang bobtail

There are two popular theories about the slang’s origin. Both have to do with animals with shortened tails.

Some believe the term was popularized by the holiday song “Jingle Bells.” There are lyrics in the song saying, “bells on bobtails ring.” This refers to the style of the horse’s tail cut — typically docked or cut short to prevent entangling with the sleigh reins.

The other theory is that the term originated from a breed of cats with short or bobbed tails. Unlike other cat breeds, bobtail cats have a shorter, stubby tail giving them the appearance of a bobcat.

Truckers might think a semi-truck without a trailer looks truncated or cut off, similar to these animals with short tails.

Bobtailing vs. deadheading

“Running bobtail” and “deadheading” are sometimes confused and used interchangeably. However, they refer to two different things.

Bobtailing is driving a freight-carrying truck without a trailer. This happens when a truck driver is on their way to pick up a loaded trailer for full truckload or less-than-truckload transport. Or, they could be returning to a terminal after unloading their trailer.

Deadheading trucks have a trailer attached, but it’s empty. For example, you’ve probably seen flatbed tractor-trailers driving on roads, transporting nothing on the empty trailer.

Both bobtail and deadheading trucks do not contain freight, so they are not generating revenue, hence the confusion.