What Is a Jackknife Semi-Truck Accident — and What You Should Do if You’re Involved

Vrdolyak Law Group
Oct 29, 2025
2 min read

Updated: Jan 15

What Is a Jackknife Accident?

A jackknife accident occurs when a semi-truck's tractor (cab) and trailer pivot into a sharp "V" or "L" shape, like a closing pocketknife. In those moments, the trailer swings sideways, often blocking multiple lanes or overturning, making control impossible for the driver.

Why Jackknife Crashes Happen

Hard or sudden braking
Loss of traction due to weather or road conditions
Speeding or following too closely
Improper loading or shifting of cargo
Mechanical failure or poor vehicle maintenance
Driver fatigue, inexperience, or impairment

Large-Truck Crash Statistics (U.S.)

5,472 fatalities in large-truck crashes in 2023 (NHTSA)
153,452 injuries in large-truck crashes in 2023 (National Safety Council)
Approximately 70% of fatalities in truck crashes are occupants of other vehicles
Fatal large-truck crashes have increased by roughly 40% over the past decade

Jackknife-Specific Safety Notes (FMCSA)

The Federal Motor Carrier Safety Administration (FMCSA) classifies a jackknife as a crash occurrence event. While fewer crashes are formally marked "jackknife," FMCSA notes that jackknife-related loss-of-control events are associated with multi-vehicle and severe crashes.

What to Do After a Jackknife Accident

1. Ensure safety and call 911

2. Document the scene (photos, DOT number, witnesses)

3. Seek medical evaluation immediately

4. Be cautious with insurance companies

5. Contact an experienced truck accident attorney such as the Vrdolyak Law Group with the skills, experience, and resources to fight big trucking every step of the way. Big trucking companies will send out teams of people to the crash site to collect evidence to prove the accident was your fault. You need a law firm that understands the importance of collecting evidence on your part, such as:

- ECM/EDR ("black box") data

- Driver logs / Hours-of-Service records

- Maintenance reports

- GPS, telematics, camera footage

Here's what semi-truck companies and drivers can do to minimize the risk of jack-knife accidents:

Train drivers properly,
Maintenance of brakes, tires, and suspension
Balanced cargo loading
Compliance with Hours-of-Service laws
ABS and stability-control systems

Why This Matters in Chicago and the Midwest

Chicago's major freight corridors (I-90/94, I-55, I-80, I-294) experience some of the highest heavy-truck volumes in the nation. Congestion, winter weather, and dense traffic increase the likelihood and severity of jackknife crashes.