A bobtail tractor, also known simply as a bobtail truck, is a semi-truck that is operating without a trailer attached. It is the tractor unit of a tractor- trailer combination when it is traveling solo, typically when moving to pick up a new trailer or after dropping off one. The term "bobtail" comes from the visual resemblance of the shorter rear end of the tractor without its trailer, similar to a bobtail cat with a shortened tail. In trucking, bobtailing refers to the act of driving the semi-truck without a trailer. This is usually a non- revenue movement since the truck isn't carrying any cargo at that time, which is less preferred in industry as it means the driver or company is not making money on that trip. Bobtail trucks have different handling characteristics compared to when they are pulling a trailer—they tend to be lighter, less stable, and require more careful braking due to the reduced weight and balance. Bobtail tractors are more maneuverable in tight spaces due to their smaller size compared to when they have a trailer attached. They are commonly seen when trucks are repositioning to pick up loads or returning after delivery. In sum, a bobtail tractor is essentially the tractor part of a semi- truck without its trailer attached, used mainly for repositioning rather than transporting cargo.