Jackknife Truck Accidents: Causes and Liability

A jackknife accident occurs when a tractor-trailer folds at the coupling — the trailer swings outward past the cab like a closing pocketknife. Once the trailer's angle exceeds roughly 45 degrees, the driver has effectively lost control, and a 53-foot trailer can sweep across several lanes of traffic in seconds, crushing or sideswiping everything in its path.

What causes a big rig to jackknife?

• Hard braking at speed. When the tractor's drive wheels lock or the trailer's momentum overruns the cab, the trailer pivots. Late braking is often a symptom of driver fatigue, speeding, or following too closely.
• Slick roads. Rain, ice, and snow reduce trailer traction; professional drivers are trained to slow well below posted limits in bad weather.
• Improperly loaded or light cargo. An unbalanced or empty trailer is far more likely to swing. Cargo securement is regulated under FMCSA rules, and the loading company may share fault.
• Brake defects or poor maintenance. Mismatched or poorly adjusted brakes cause uneven braking force between tractor and trailer — see brake failure accidents.
• Curves and downgrades taken too fast. Speed management on grades is a core commercial driving skill.

Who can be held liable?

Jackknifing is almost always preventable, which is why these cases often come down to proving which failure started the chain:

• The driver — speeding, tailgating, or braking improperly for conditions
• The trucking company — negligent training, unrealistic schedules, or poor maintenance programs
• The cargo loader — unbalanced or unsecured freight
• A maintenance contractor or manufacturer — defective brakes, tires, or coupling components

A big rig truck accident lawyer will typically retain an accident reconstruction expert and pull the truck's event data recorder, which captures speed, brake application, and steering input in the seconds before the crash. Learn how this evidence works on our FMCSA regulations & evidence page.

Injuries and compensation

Because a jackknifing trailer strikes vehicles broadside or crushes them against barriers, injuries are frequently catastrophic — brain injuries, spinal damage, and fatalities. Compensation can include medical care, lost earnings, pain and suffering, and in fatal cases, wrongful death damages. See what a truck accident settlement covers, or start a free case review now.