Semi-Truck Underride Crashes: The Deadliest Truck Collision and Who Is Liable

Published July 20, 2023 · Injury Law Basics

It happens in a fraction of a second. A tractor-trailer pulls across a dark two-lane road, or sits half on the shoulder of I-75 with no flashers, and a car that cannot stop in time slides underneath the trailer. The bumper, the hood and the crumple zones the car was engineered around pass beneath the trailer's frame, and the first thing the trailer strikes is the windshield and the people behind it.

That is an underride crash. Among the collisions we see between passenger vehicles and commercial trucks, it is the one most likely to end in a funeral or a catastrophic head and neck injury. It is also the kind of case where the evidence that decides liability can be gone within days.

Why underride is so lethal

A modern car is designed to absorb a crash with its front end. The bumper, frame rails and engine compartment crumple to slow the occupants down, and the airbags deploy on a timing calibrated to that crush. A semi-trailer's floor sits roughly at the height of a car's hood. Unless something at bumper level stops the car, it keeps going until the trailer meets the passenger compartment, often at the A-pillars and roof.

There are two main types:

• Rear underride: a car strikes the back of a trailer that is stopped, slowing, or moving well under the speed of traffic.
• Side underride: a car strikes the side of a trailer that is turning, backing into a driveway, or crossing the road, often at night.

What federal rules require, and what they do not

Federal motor carrier regulations require most trailers and semitrailers manufactured since January 26, 1998, to carry a rear impact guard, the steel bar hanging below the back of the trailer. Under 49 C.F.R. 393.86, the guard must meet the federal vehicle safety standards for strength and energy absorption (FMVSS Nos. 223 and 224), must extend to within four inches of the sides of the trailer, and must hang no more than 22 inches above the ground. Those requirements apply for the life of the trailer, so a guard that is bent, rusted, cut away or poorly repaired is a violation, and 49 C.F.R. 396.3 requires carriers to systematically inspect, repair and maintain their equipment.

Trailers must also be conspicuous. Federal rules require red-and-white retroreflective sheeting, the reflective tape you see along the sides and rear, so that a trailer stretched across a road at night reflects headlights. (See, for example, 49 C.F.R. 393.13, which governs older trailers and points to the FMVSS No. 108 conspicuity standard for newer ones.) Missing, dirty or faded tape is evidence.

And when a truck stops on the traveled road or the shoulder for anything other than a necessary traffic stop, 49 C.F.R. 392.22 requires the driver to turn on the hazard flashers immediately and to place warning triangles within ten minutes, at set distances behind the truck. A trailer parked on the shoulder in the dark without flashers or triangles is a hazard the regulations were written to prevent.

What the federal rules do not require, as of this writing, is a side underride guard. Side guards exist and are used on some trailers, but no federal standard mandates them. That does not mean a side underride crash is nobody's fault. It means the case is built on the driver's conduct, the trailer's visibility, and, sometimes, the design choices of the manufacturer.

Who may be liable

Because underride involves both a driving decision and a piece of equipment, we evaluate these cases as both trucking cases and product cases. The possible defendants include:

• The truck driver, for pulling across traffic without a safe gap, stopping in a travel lane, failing to use flashers and triangles, or driving while fatigued.
• The motor carrier, which is responsible for its driver's conduct on the job and for its own failures: inadequate training, pushing schedules that violate hours-of-service rules, and neglecting guard and lighting maintenance.
• The trailer owner or lessor, if different from the carrier, and any maintenance shop that inspected or repaired the guard.
• The trailer manufacturer, if the guard's design was inadequate. Under Ohio's Products Liability Act, R.C. 2307.75 asks whether the foreseeable risks of a design outweighed its benefits, and whether a practical, technically feasible alternative design was available that would have prevented the harm. Stronger guard designs that perform better in offset crashes, and side guards, are part of that conversation.

Ohio's comparative-fault rules apply, and the trucking company's insurer will almost always argue that the car's driver should have seen the trailer. That argument is weaker when the trailer was unlit, the tape was missing, the truck blocked the road with no warning, or the guard failed in a crash it should have survived. Proving those facts requires the physical evidence.

The evidence that disappears

Underride cases are won or lost on evidence that the trucking company controls:

• The trailer and its guard. Once a trailer is repaired or returned to service, the bent guard and its welds are gone. The guard needs to be inspected, measured and photographed before anyone touches it.
• Electronic logging device (ELD) data and telematics, which show hours of service, speed and hard-braking events.
• Forward- and driver-facing camera footage, which many fleets record and overwrite on a schedule.
• Maintenance and inspection records for the trailer, including the guard and lighting.
• The car's own event data recorder, which shows speed and braking in the seconds before impact.

Our chapter on gathering evidence while it still exists explains why a preservation letter to the carrier has to go out within days, not weeks. Trucking companies often send investigators to the scene within hours. The injured person's family deserves the same urgency.

What this means for you

If someone you love was hurt or killed when their car went under a trailer, the questions to ask are not only "who hit whom" but "why didn't the guard stop the car" and "why couldn't the driver see the trailer." The answers often point to more than one defendant and to commercial insurance policies far larger than an ordinary driver carries. We explain how truck crash claims in Dayton differ from car crashes, and how our car and truck accident practice handles them.

Dayton sits where I-75 and I-70 cross, and as I wrote in our post on Dayton's truck corridors, heavy freight traffic runs through the Miami Valley around the clock. For families who have lost someone, our wrongful death page explains who can bring the claim and what it can recover.