A tractor jackknife occurs when what happens?

A tractor jackknife occurs primarily when the trailer swings out sideways relative to the tractor unit, typically as a result of loss of traction in the drive wheels. When the drive wheels lose traction, particularly in slippery conditions or during sudden braking, the rear of the truck can slide sideways while the front is still moving forward. This creates a scenario where the trailer can pivot around the connection point with the tractor, resulting in a jackknife situation.

In this scenario, maintaining control is crucial, as the vehicle can rotate into a dangerous position, leading to more severe accidents. Understanding this phenomenon is essential for truck drivers because it emphasizes the importance of maintaining proper speed, ensuring adequate traction, and recognizing the potential for loss of control, especially in adverse conditions.