Why should the trailer hand brake not be used to straighten out a jackknifing trailer?

Using the trailer hand brake to straighten out a jackknifing trailer is inadvisable because it can exacerbate the jackknifing situation. In the event of a jackknife, the angle between the cab and the trailer becomes too sharp, which leads to instability and potential loss of control. Engaging the trailer hand brake can actually increase the angle of the jackknife, making the situation worse by causing the rear wheels of the trailer to lock up. This locking can prevent the trailer from following the path of the towing vehicle, leading to further loss of control and increasing the risk of a rollover or additional accidents.

The dynamics of a jackknife situation already introduce severe instability; applying the hand brake disrupts the natural corrective forces that could help realign the trailer. Instead, the focus should be on steering and accelerating gently to straighten the rig. Understanding this principle is crucial for safe driving and for managing emergency situations effectively.