Jack-knifing occurs when either the tractor loses traction and is pushed sideways by the trailer, or the trailer loses traction and begins to swing around the tractor. Most Jack-knifes occur when the driver applies too much braking and causes the drive tires to slide, or when braking occurs while steering. If the alignment between the tractor and trailer is not straight, when braking occurs, the trailer will try to push the tractor sideways.
Steer gently. Most jack-knifes occur when the driver tries to steer out of the control loss and over compensates. This causes the truck to react more violently and is even harder to control. Remember, if the angle between your tractor and your trailer exceeds 15 degrees, it is unlikely that you will be able to recover.