What is a "jackknife" condition in combination vehicles?

The term "jackknife" condition in combination vehicles refers to a situation where the trailer swings out toward the tractor, forming an angle that resembles that of a folding pocket knife. This typically occurs when the vehicle is losing traction, often due to sudden braking or sharp turning while in motion. When the trailer begins to pivot towards the cab, it can significantly increase the risk of a dangerous situation, including loss of control or rollover.

This movement is generally caused by a lack of traction on the trailer wheels or improper braking techniques, which may lead to the trailer exceeding its intended path. Understanding this concept is crucial for drivers of combination vehicles because recognizing and managing near-jackknife situations can help maintain control and ensure road safety.