What can cause jackknifing in a trailer?

Jackknifing occurs when the trailer swings out to the side of the truck, creating a V-shape, which can lead to a loss of control. Poor braking techniques, particularly the improper use of retarders, are a significant contributing factor in jackknifing. This happens because if the truck driver applies the brakes abruptly or unevenly, it can cause the wheels of the trailer to lock up or decelerate at a different rate than the tractor. When this occurs, the momentum of the trailer may cause it to slide sideways, leading to a jackknife situation.

In the context of the other factors, while improper load distribution can affect stability, excessive speed can lead to a loss of control generally, and wet road conditions increase the likelihood of skidding, it is the application of brakes, particularly when utilizing retarders incorrectly, that directly sets up the conditions for jackknifing by causing the trailer to lose traction relative to the tractor. These elements, while they can contribute to overall instability, do not specifically cause jackknifing in the same direct manner as poor braking techniques.