According to Iron Horse Transport, a jackknife occurs when a truck’s trailer swings out from behind it,
causing the truck to form an angle like a pocket knife. It is a type of
skid, and when it occurs, the driver has lost control. In some cases, the
axles on the trailer lock, causing the trailer to drag with locked brakes.
The most common causes of jackknives include the following:
Poorly maintained brakes
High speeds followed by slamming on the brakes
Inclement weather and slippery conditions, due to loss of
traction leading to a shift in the truck’s weight
Sharp turns, especially at high speeds