A commercial truck jackknifes when the cab and trailer create an acute angle, resulting in an L or V shape. Jackknifing happens when the cab wheels or trailer wheels lose traction. Slamming on brakes and causing the axles to lock, driving too fast to allow for adequate response time to hazards, curvy roads, slippery roads, empty trailers, and improperly secured cargo can all cause the loss of traction.
A truck jackknife often causes serious injuries to other drivers on the road who either crash into the truck or another vehicle when trying to avoid the truck.