Why do trucks jackknife?

| Oct 27, 2020 | Personal Injury |

Driving near large trucks can be intimidating; it can be difficult to maneuver around their massive size and they take longer to slow down than smaller passenger vehicles.

However, things get a whole lot scarier when you’re traveling 60 mph on the highway and the truck in front of you begins to lose control. The truck driver is often at the mercy of the vehicle he’s trying to operate; that much weight traveling at that much speed makes regaining control almost impossible. For this reason, large trucks are involved in thousands of auto accidents each year.

However, a runaway truck becomes even more unpredictable if it enters a jackknife position. A jackknife position occurs when the cab of a semi-truck and its trailer swing in opposite directions causing the rig to fold.


Jackknife accidents can occur suddenly and for many different reasons, but they are more likely to happen under certain circumstances.

  • Inclement weather: Jackknife accidents happen when the driver loses control and the truck begins to skid and turn sideways. Wet or icy can cause the truck to slide or skid, increasing the odds of a jackknife.
  • Light loads: Trucks tend to jackknife while carrying lighter loads. An emptier trailer means a less stable trailer and one that is more prone to swinging.
  • Bad brakes and/or bald tires: Worn out breaks and bald tires can cause a truck to skid, especially on wet or icy roads.
  • Overcorrection: It’s tempting for many truckers to jerk the steeling wheel to regain control of the truck, but if this is done to suddenly the truck may turn sideways and a jackknife may ensure.
  • Turning too sharply: Entering a turn to quickly or at too great a speed could cause the truck to swerve and the trailer to swing.

Although jackknifes can result in catastrophic damage, both truckers and drivers can take steps to avoid them.

Truckers can take simple precautions like ensuring the trailer is carrying sufficient weight to reduce the likelihood of swings. They should also have their truck regularly examined for break and tire deficiencies.

Drivers on the other hand should always stay a safe distant from semi-trucks while on the road. A good rule of thumb is that if you can’t see the trucks side mirrors you’re took close. Keeping a safe distance gives the truck time to react and, if a jackknife does occur, keeps the car out of the swinging trailer’s reach.