An 18-wheeler consists of two parts: the tractor and the trailer. The tractor contains the engine and it tows the trailer, which holds the cargo. The trailer is not hitched to the back of the tractor, but rather to a point forward of the tractor’s rear axle. The tractor therefore bears some of the trailer’s weight, which helps keep the two parts stable. Despite this feature, a fully loaded 18-wheeler can weigh as much as 80,000 pounds. The sheer force of such a vehicle can be catastrophic in an accident. Where an automobile accident between two similarly sized vehicles can be highly destructive, it cannot compare to a collision between a car and an 18-wheeler. Such crashes can cause serious disabling injuries, injury to the brain or spinal cord, or even death.
A danger unique to 18-wheelers is jackknifing. This is when the tractor skids or otherwise loses grip on the road and the weight of the trailer causes the trailer to spin forward. The motion resembles a pocketknife folding closed, hence the term “jackknifing.” A jackknifing 18-wheeler is nearly impossible to control, and it is impossible for the driver to move once it comes to a stop.