Underride Accidents

What Is an Underride Crash?

An underride crash happens when a passenger car, pickup, or SUV collides with a truck or trailer and slides underneath it. Because the trailer bed sits higher than a car’s hood and windshield, the smaller vehicle’s crumple zones, airbags, and seatbelt systems are rendered useless. The roof of the car is often sheared off or crushed inward, causing catastrophic head, neck, and chest injuries — or instant death.

There are two primary types of underride collisions:

Rear Underride

Rear underride occurs when a vehicle strikes the back of a truck trailer. This is the more commonly recognized type and has been subject to federal regulation since 1953. Current NHTSA regulations require rear underride guards on trailers, but the standard — last updated in 2022 — has been criticized by the Insurance Institute for Highway Safety (IIHS) as insufficient. IIHS has stated that “NHTSA’s updated rule does not go far enough to be meaningful” and that most newly manufactured guards already met the new standard before it was adopted.

Side Underride

Side underride happens when a vehicle strikes the side of a truck trailer — typically at an intersection, during a lane change, or when a truck makes a wide turn. There are currently no federal regulations requiring side underride guards. According to a 2024 NHTSA report to Congress, the agency estimates approximately 89 fatalities annually from side underride crashes within the scope of potential regulation — but IIHS research suggests the true number is far higher, estimating that side guards could prevent 159 to 217 deaths per year.

Why Underride Guards Are Inadequate

The history of underride regulation in the United States is a story of industry resistance and regulatory delay. Federal rear-guard standards were first adopted in 1953, strengthened slightly in 1998, and updated again in 2022 — but safety researchers have consistently found them insufficient.

The IIHS TOUGHGUARD program tests rear underride guards in three crash configurations and awards recognition to guards that prevent underride in all scenarios. Several major trailer manufacturers now build guards that exceed the federal standard — proving that stronger protection is both technically feasible and commercially viable.

Side underride protection remains the bigger gap. Despite decades of research showing that side guards can prevent fatalities at impact speeds up to 40 mph, NHTSA has not required them. A 2024 NHTSA cost-benefit analysis estimated that side guards would save 17 lives per year — but IIHS research found this estimate to be “dramatically” low, arguing the true benefit is more than 10 times higher.

Injuries in Underride Crashes

The injuries from underride collisions are among the most severe in all of motor vehicle crash types. Because the trailer bypasses the vehicle’s safety systems, occupants sustain injuries including:

• Traumatic brain injuries — The roof intrusion common in underride crashes causes direct head impacts
• Spinal cord injuries — Compression and shearing forces on the spine often result in paralysis
• Decapitation and partial decapitation — The leading edge of the trailer can shear through the windshield at occupant head height
• Crush injuries to the chest and abdomen — The collapsing roof compresses occupants against the dashboard and steering column
• Amputations — The violent intrusion of the trailer into the vehicle cabin can sever limbs

Survivors of underride crashes often face lifetime catastrophic injuries requiring ongoing medical care, adaptive equipment, and full-time personal assistance.

Liability in Underride Crash Cases

Underride crash claims can target multiple liable parties:

• The truck driver — For actions contributing to the crash (running a red light, making an unsafe lane change, driving without proper lights at night)
• The motor carrier — For failing to equip trailers with adequate underride protection, or for operational decisions that created the crash conditions
• The trailer manufacturer — If the underride guard was defectively designed, manufactured below applicable standards, or known to fail in foreseeable crash types
• The guard manufacturer — If the underride guard itself was defective or failed to perform as designed

In cases where the trucking company or manufacturer knew their underride protection was inadequate and failed to act, Kentucky courts may award punitive damages on top of compensatory damages.