As a driver working in the trucking industry there will be times when you will have to drive a truck minus a trailer. A truck weighing over 10,000 lbs. without a trailer is defined as a bobtail. Driving a truck bobtail is somewhat different from pulling a trailer behind you, and at times, it can be more difficult. As a professional driver you will need to learn how to operate the truck safely without a trailer. When you drop one trailer and hook to another it is also considered "bobtailing." A box, short straight truck or short flatbed truck is sometimes incorrectly referred to as a bobtail. These trucks do not have a separate trailer attached.
Connect the air lines couplings (gladhands) and the electrical coupling (pigtail) to the dummy mounts on the back of the truck cab. The purpose of this is to reduce the likelihood of dirt and grease getting into the electrical connectors. It will also prevent you from accidentally pulling the airlines and pigtail assembly from the truck with the drive tandems.
Depress only the yellow air valve to release the tractor brakes. The red valve is for the trailer brakes and if it is depressed while there is no trailer attached, air will be supplied to the system and you will hear the sound of air escaping through the air line.
Place the truck into either second or third gear and proceed gradually. The truck may lurch forward because the tractor is much lighter than a truck and loaded trailer.
The actual maneuvering of a bobtail is very similar to operating a car, especially in regard to backing. When backing a combination vehicle, the driver steers in the opposite direction as he would when backing a car; however, to back a bobtail, the driver would steer the same as if he were operating a car.
Apply brakes gently, because without the presence of a trailer, the rear axles may skid to one side.