A jackknife accident occurs when a commercial truck’s trailer swings outward at an angle from the cab, forming a shape similar to a folding pocketknife. These crashes are among the most dangerous types of truck accidents because they can block multiple lanes of traffic, trigger chain-reaction collisions, and cause catastrophic injuries.

Jackknife accidents fall under truck accident law, a specialized area of motor vehicle accident law that involves federal trucking regulations, commercial insurance policies, and complex liability questions. Unlike ordinary car accidents, jackknife crashes often raise issues related to braking systems, cargo loading, driver training, and regulatory compliance.

This page explains how jackknife accidents happen, how fault is determined, and the legal rights and responsibilities of both injured motorists and truck drivers.

A jackknife accident typically occurs when:

• A truck’s cab slows or stops suddenly while the trailer continues moving
• The trailer swings sideways, overtaking or blocking the cab
• The truck loses directional control and spans across lanes

Jackknife accidents most commonly involve tractor-trailers, but can also occur with delivery trucks or vehicles towing heavy loads.

Jackknife accidents are rarely the result of a single factor. Common contributing causes include:

• Sudden or improper braking
• Slippery road conditions (rain, snow, ice)
• Speeding for weather or traffic conditions
• Improperly loaded or unbalanced cargo
• Mechanical failures, including brake defects
• Driver fatigue or inexperience

In some cases, another motorist’s sudden maneuver, such as cutting in front of a truck, may contribute to the loss of control.

Potentially Liable Parties

Liability in jackknife accidents may extend beyond the truck driver and include:

• The trucking company or motor carrier
• Cargo loading or shipping companies
• Maintenance or repair providers
• Vehicle or brake manufacturers
• Other drivers who triggered the loss of control

Fault is determined through negligence analysis, regulatory compliance review, and causation evidence.

For passenger-vehicle occupants injured in a jackknife accident, legal claims often focus on:

• Whether the truck driver operated safely for conditions
• Compliance with federal hours-of-service rules
• Proper cargo loading and securement
• Adequate vehicle maintenance and inspections
• Employer responsibility for driver conduct

Jackknife accidents frequently involve multiple injured parties, which can complicate insurance claims and settlement negotiations.

Truck drivers involved in jackknife accidents face distinct legal challenges, including:

• Defending against automatic fault assumptions
• Demonstrating compliance with safety regulations
• Addressing employer pressure related to delivery schedules
• Navigating internal company investigations
• Protecting employment and licensing status

Truck drivers may also be injured in jackknife crashes and may have rights under workers’ compensation or third-party liability claims, depending on the circumstances.

Because jackknife accidents often block roadways, they frequently result in multi-vehicle collisions. Legal issues in these cases may involve:

• Determining the initiating cause of the crash
• Allocating fault among multiple drivers
• Assessing whether subsequent impacts were unavoidable
• Coordinating multiple injury claims

Accident reconstruction and timing analysis are often essential in resolving these disputes.

Jackknife accidents often cause more severe and complex injuries than standard vehicle crashes due to the size of commercial trucks, the sideways movement of the trailer, and the likelihood of multiple secondary impacts.

Because these crashes frequently involve high-speed deceleration and lateral force, injured occupants may suffer traumatic brain injuries, spinal damage, orthopedic fractures, internal injuries, or crush injuries caused by vehicle intrusion or trailer impact.

From a legal perspective, these injuries matter not only because of their severity, but because they often:

• Involve delayed or progressive symptoms
• Require long-term or future medical care
• Support claims for permanent impairment or reduced earning capacity

In jackknife cases, injury claims are commonly scrutinized by commercial insurers. Recovery often depends on early medical documentation, diagnostic imaging, and expert opinions linking the injuries to the crash mechanics and sequence of impacts.

Jackknife accidents often overlap with other truck accident categories, including:

Correctly identifying the accident type helps determine applicable legal standards and responsible parties.

Jackknife accidents typically result from sudden braking, loss of traction, or improper cargo balance, and they often involve multiple contributing factors.

The articles below examine how jackknife accidents occur, how fault is assessed, and what evidence is commonly used to investigate these crashes.

Jackknife accidents are among the most complex and dangerous truck crashes, often involving multiple vehicles, serious injuries, and layered liability. Determining fault requires careful analysis of driver conduct, vehicle condition, cargo handling, and regulatory compliance.

Understanding how jackknife accidents are evaluated under truck accident law can help injured individuals and truck drivers better understand their legal rights and potential next steps following a crash.