Truck Underride Crashes: How Federal Guard Standards Have Changed and What They Mean for Victims

An underride crash happens when a passenger vehicle collides with the rear or side of a large truck trailer and slides underneath it. Because a trailer's bed sits well above the hood of most cars, the trailer can strike the passenger compartment directly — bypassing the car's crumple zones, airbags and other safety systems designed to absorb the force of a crash. The results are frequently catastrophic or fatal, even at moderate speeds.

For years, safety advocates — many of them families who lost loved ones in underride crashes — pushed for stronger protections. Congress responded in the Infrastructure Investment and Jobs Act of 2021 by directing federal regulators to update rear underride guard standards, require annual inspections of rear guards, and study side underride guards. In 2022, the National Highway Traffic Safety Administration (NHTSA) issued a final rule upgrading the federal rear impact guard standards. This article explains these developments and what they mean for people injured in underride crashes.

What Underride Guards Do

Underride guards — sometimes called rear impact guards or "Mansfield bars" — are steel bars mounted on the back of trailers. Their purpose is to stop a passenger vehicle from sliding under the trailer in a rear-end collision, allowing the car's own safety systems to work.

Rear guards have been required on most trailers for decades, but the original federal standards were criticized as inadequate. Crash testing by the Insurance Institute for Highway Safety (IIHS) showed that many guards meeting the older federal standard could fail in certain crashes, especially when the car struck the trailer off-center, near the edge of the guard. Some trailer manufacturers voluntarily improved their designs to perform better in these tests.

The Updated Rear Guard Standard

The 2022 final rule upgraded the federal standards governing rear impact guards on trailers and semitrailers. In general, it aligned U.S. requirements more closely with the stronger Canadian standard, which requires guards to absorb more energy and to prevent underride in crashes at higher speeds. The rule applies to newly manufactured trailers subject to the standard, with a compliance date that followed its issuance.

Safety advocates welcomed the update but argued that it did not go far enough, pointing to guards that performed even better in independent testing. The debate over how strong guards should be — and how they should perform in offset crashes — continues.

Annual Inspections

The 2021 infrastructure law also directed the Federal Motor Carrier Safety Administration (FMCSA) to include rear impact guards in required annual commercial vehicle inspections. A rear guard that is bent, cracked, corroded or missing may not protect anyone in a crash. Including guards in inspections helps ensure that they are maintained throughout a trailer's life.

For injury claims, inspection records can be important evidence. If a guard was damaged before a crash and the motor carrier failed to repair it, that failure may support a claim of negligence.

Side Underride: The Unresolved Question

Side underride crashes occur when a vehicle strikes the side of a trailer — often when a truck is turning, crossing an intersection, or pulling out of a driveway, especially at night when the side of a trailer may be hard to see. Unlike rear guards, side guards are not currently required on trailers in the United States.

The infrastructure law directed NHTSA to research side underride guards and established an advisory committee on underride protection to provide recommendations. The committee's work has addressed the potential benefits of side guards, their costs, their effect on trailer operations, and design considerations. Some trailers are equipped with side skirts for fuel efficiency, but aerodynamic skirts are not designed to stop a car from sliding under the trailer.

Whether and when side guards will be required remains an open question. Families of victims, safety organizations and the trucking industry continue to debate the issue.

Why Underride Crashes Happen

Common circumstances in underride crashes include:

• A truck slowing or stopping suddenly on a highway without adequate warning
• A truck parked on a shoulder or roadway without proper lighting or reflective devices
• Poor visibility at night, in fog or in rain
• Trailer lights or reflective tape that are dirty, damaged or missing
• A truck making a wide turn or crossing a highway in front of oncoming traffic
• A truck backing across a road or into a driveway
• Inadequate or damaged underride guards

In many cases, more than one factor contributes. A driver may be partly at fault for following too closely, while the trucking company may be at fault for poor maintenance or an unsafe maneuver.

Who May Be Responsible

Underride cases often involve multiple potentially responsible parties:

The Truck Driver

A truck driver may be negligent for stopping unsafely, failing to use hazard warning devices, making an unsafe turn, or driving while fatigued or distracted.

The Motor Carrier

Trucking companies are responsible for maintaining their equipment, including lights, reflectors and underride guards. They are also responsible for hiring qualified drivers, training them, and enforcing hours-of-service rules.

The Trailer Manufacturer

If an underride guard failed because of a defect in its design or manufacture, the trailer manufacturer may be responsible under product liability law. Crash testing data and engineering analysis are often central to these claims.

Maintenance Providers

Companies that inspected or repaired the trailer may be responsible if they failed to identify or fix a damaged guard or lights.

Other Drivers

In some crashes, another vehicle contributed — for example, by cutting off the passenger vehicle or causing the truck to stop suddenly.

Evidence in Underride Cases

Because underride cases often turn on technical questions, evidence must be preserved quickly. Important evidence may include:

• The trailer and its rear guard, which should be preserved and not repaired or scrapped
• Photographs and measurements of the guard and the crash damage
• Inspection and maintenance records for the trailer
• Electronic logging device records and other hours-of-service data
• Truck event data recorder and telematics data
• Dash camera footage from the truck or other vehicles
• Lighting and conspicuity evidence, such as the condition of reflective tape
• Police crash reconstruction reports
• Manufacturer specifications and testing data for the guard

A preservation letter sent promptly to the motor carrier, its insurer and any tow or salvage company can help prevent the loss of this evidence.

Injuries in Underride Crashes

Because the trailer can intrude into the passenger compartment, injuries in underride crashes tend to be severe:

• Traumatic brain injuries
• Head and facial injuries
• Neck and spinal cord injuries
• Crush injuries
• Fatal injuries

Families who lose loved ones in underride crashes may bring wrongful death claims, and the estate may bring a survival claim for the decedent's losses before death, depending on state law.

Insurance and Compensation

Commercial motor carriers are required to carry higher minimum levels of liability insurance than private drivers, and many carry additional coverage. Trailer manufacturers and maintenance providers may have their own insurance. Identifying all responsible parties and policies is essential in cases involving catastrophic injuries or death, where losses can be very large.

Compensation in underride cases may include medical expenses, future care, lost income and earning capacity, pain and suffering, and, in fatal cases, damages available to the family under wrongful death law.

What Families Can Do

Families affected by underride crashes have been at the center of advocacy for stronger standards. Beyond legal claims, many have participated in public comment on rulemaking, supported research, and shared their stories to raise awareness. Legal claims can also bring accountability and, in some cases, prompt companies to change practices.

Conspicuity: Making Trailers Visible

Many underride crashes happen because a driver did not see a trailer until it was too late, particularly at night. Federal rules require trailers to have reflective sheeting, commonly called conspicuity tape, and specified lighting to make them visible in the dark. Over time, reflective tape can fade, peel or become covered with dirt, and lights can burn out or be damaged. Motor carriers are responsible for maintaining these safety features.

In an underride case, the condition of a trailer's lighting and reflective markings at the time of the crash can be important evidence. Photographs taken at the scene, post-crash inspections, and maintenance and inspection records can help establish whether the trailer was adequately visible.

Trucks Stopped on Highways

Another common underride scenario involves a truck stopped or moving very slowly on a highway or shoulder. Federal rules require drivers of stopped commercial vehicles to activate hazard warning lamps and, within a short time, place warning devices such as reflective triangles at specified distances behind the truck. A truck stopped in a travel lane at night without proper warnings can create an extreme hazard for approaching drivers.

When a driver stops for reasons that could have been avoided — such as running low on hours, missing an exit, or making a delivery from the roadway — those decisions may also be scrutinized.

Trucks Crossing or Turning Across Highways

Side underride crashes frequently occur when a tractor-trailer pulls across a highway from a side road or driveway, or makes a wide turn, blocking lanes with the length of its trailer. Approaching drivers, particularly at night, may not recognize the trailer as an obstacle until it is too late. Questions in these cases often focus on whether the truck driver had adequate time and visibility to cross safely, whether the truck's lights and reflective markings were adequate, and whether the location itself — such as a facility entrance on a high-speed road — was designed safely.

The Role of Crash Reconstruction

Reconstructing an underride crash typically requires specialized expertise. Reconstructionists analyze vehicle damage, the depth of intrusion into the passenger compartment, skid marks and gouge marks, vehicle data, lighting and sight-line evidence, and the guard's deformation. Engineers may evaluate whether the guard met applicable standards and whether a better-designed guard would have prevented underride. These analyses can determine whether claims against the trailer manufacturer are viable in addition to claims against the driver and motor carrier.

Frequently Asked Questions

My loved one was driving and hit the back of a truck. Doesn't that mean they were at fault?

Not necessarily. Even in rear-end underride crashes, the truck may have been stopped unlawfully, lacked proper lighting or warnings, or had a defective or damaged guard. And even if the passenger vehicle driver was partly at fault, a better guard might have prevented a fatal injury. Comparative fault rules in many states allow recovery to be apportioned.

What is a crashworthiness claim?

A crashworthiness claim argues that a product failed to provide reasonable protection in a foreseeable crash, making the injuries worse than they would otherwise have been. Underride guard claims often rely on this theory.

Should the trailer be preserved?

Yes. The trailer and its guard are often the most important evidence. A preservation letter should be sent as soon as possible.

Are older trailers held to the new rear guard standard?

Updated manufacturing standards generally apply to trailers built after the compliance date. Older trailers remain subject to the standards in effect when they were made, but carriers must still maintain guards in good condition, and inspection requirements apply. The age and condition of the guard may both be relevant.

Key Takeaways

• Underride crashes occur when a car slides under a truck trailer, often causing catastrophic or fatal injuries.
• Federal law has strengthened rear underride guard standards and requires guards to be included in annual inspections.
• Side underride guards are not currently required in the United States and remain under study.
• Truck drivers, motor carriers, trailer manufacturers and maintenance providers may share responsibility.
• Preserving the trailer, its guard and electronic data quickly is critical to any claim.

How We Can Help

At Personal Injury Lawyer Pro, our truck accident attorneys investigate underride crashes with qualified reconstruction and engineering professionals, preserve critical evidence, and pursue every responsible party. If you or a loved one was hurt — or a family member was killed — in a truck crash, contact us for a free, confidential consultation. You pay no attorney fee unless we recover compensation for you.