Jackknifing occurs when the trailer of a big rig or other articulated vehicle loses traction and skids sideways, forming an L or V shape with the tow vehicle. Here is an explanation of how to prevent it.
Watch for trailer swing, especially when braking, turning, and changing lanes. By keeping close tabs on the trailer, it may be possible to recognize and prevent jackknifing before it actually happens.
Keep both vehicle and trailer properly maintained. Worn-out tires and bad suspension components increase the risk of losing control.
Follow the manufacturer's recommendations for loading capacity of trailer and tow vehicle. Never drive with an overloaded or unbalanced trailer.
Be wary of light loads. In many cases, the trailer involved in a jackknifing incident was in fact empty. The vehicle and trailer brakes are designed for a full load, and are far too potent for an underweight trailer. When strong brakes are applied, the lighter trailer locks up and thus only needs a small input to begin skidding sideways.
Invest in anti-jackknife systems for your tow vehicle and trailer. Modern antilock trailer braking systems can sense tire skid and automatically adjust braking force to prevent lockup.