What does "jackknifing" mean in the context of driving?

In the context of driving, "jackknifing" refers to a situation where the tractor unit of a truck turns at a sharp angle to the trailer, typically resulting in a configuration that resembles a folded knife. This usually occurs when the trailer skids sideways and the tractor does not follow in a straight line, creating a dangerous scenario where the two parts of the truck are at an acute angle to each other.

This phenomenon can happen in slippery conditions or when sudden braking occurs, causing loss of control. It is particularly relevant for truck drivers to understand because jackknifing can lead to severe accidents and is a significant risk especially when driving with a heavy load or during adverse weather conditions.

Other options reflect potential safety issues relevant to driving but do not capture the specific mechanics of a jackknife situation. For instance, improperly securing cargo and driving with an uneven load might lead to different handling issues but are not directly related to the angle at which the tractor and trailer can misalign. Similarly, failing to steer correctly in adverse conditions is a broader driving response that could lead to a jackknife scenario but doesn't define what jackknifing itself is.