The Legislative and Regulatory History of Underride Guards

Michael GrossmanMarch 03, 2023 4 minutes

Underride guards have been a mandatory piece of safety equipment on commercial trucks since the 1950's, but simple as they may seem the rules behind their use and design have had some odd twists and turns over the years.

In this article we'll look at that history, what the future may hold, and what that means for victims of underride accidents.

A Brief Timeline of Underride Guard Legislation and Regulation


The National Transportation Safety Board (NTSB) introducee the first standards meant to prevent underride accidents. The regulations required vehicles with cargo beds 30 or more inches off the ground, including both straight trucks and semi-trailers, to have underride guards bolted or welded underneath. The guards also must cover the area within 18 inches of the vehicle sides.

The rules didn't extend much beyond that, and exempted many kinds of commercial vehicle (pulp trailers, log trucks, tractors, tow trucks, any vehicle with a cargo bed lower than 30 inches, and others) from compliance. To this day straight trucks are still only expected to conform to the '53 standards, but tractor-trailer requirements got a second look the following decade.


Famous actress Jayne Mansfield was riding in a Buick Electra with her lawyer and another man when the car rear-ended a tractor-trailer near Biloxi, Mississippi. The impact killed all three adults; Mansfield's three children, asleep in the back seat, survived with minor injuries.

The starlet's violent death caused major public outcry, prompting the National Highway Traffic Safety Administration (NHTSA) to recommend changes to underride guard standards. The matter was debated and proposals were made before Congress, but no legislative or regulatory action was taken. People started calling underride guards "Mansfield bars" in honor of the late actress.


A study by the Insurance Institute of Highway Safety (IIHS) demonstrated the inadequacy of 1953's standards for rear underride guards. A Senate hearing led to new calls for stronger underride protections; changes were drafted but not implemented. Multiple studies over the next 20 years showed that serious and fatal underride collisions were drastically under-reported and a more significant issue than previously thought, but no legislative or regulatory action was taken.


The federal safety standards for underride protection devices were finally updated, but applied only to trailers & semi-trailers that were manufactured after January 26, 1998. Codified in Federal Motor Vehicle Safety Standards 223 (installation of underride guard) and 224 (guard strength and testing standards), the new rules reduced the guard's required height to 22 inches from its former 30 inches. Many of the vehicle types originally exempted in 1953 continued to be omitted from the regulations.

2009 - 2013

Multiple studies from the IIHS and other agencies demonstrated that 1996's federal underride guard updates were largely inadequate. Studies found guards often failed to prevent underride, and most related crashes resulted in serious injury or fatality.

2017 - 2021

Senators introduced the Stop Underrides Act, aimed at increasing federal standards for rear underride guards and implementing specific policies about side and front guards on commercial trucks. The bill also required commercial drivers to examine rear, side, and front underride guards during pre-trip inspections. It was reintroduced in 2019 and 2021 and got referred to the Committee on Commerce, Science, and Transportation for further study.


In response to stipulations in the Biden Administration’s Infrastructure Investment and Jobs Act (IIJA), the NHTSA issued a final rule requiring improved strength standards for rear underride guards. According to the rule,

Adopting these standards will require rear impact guards to provide sufficient strength and energy absorption to protect occupants of compact and subcompact passenger cars impacting the rear of trailers at 56 kilometers per hour (km/h) (35 miles per hour (mph)). Upgraded protection will be provided in crashes in which the passenger motor vehicle hits: the center of the rear of the trailer or semitrailer; and, in which 50 percent of the width of the passenger motor vehicle overlaps the rear of the trailer or semitrailer.

87 FR 42339

The rules became official in January of 2023 and industry compliance is expected by mid-2024. They are the most current finalized regulations about underride accidents.

What Might Happen with Underride Legislation in the Future?

If the past 70 years are any indication, the most likely path of future underride guard legislation is decades of talk punctuated by occasional action. However, as research shows the pitfalls of current underride protection hopefully some stronger regulation and even some inventive technological improvements are on the horizon.

Whatever the future might hold, though, hundreds of people are currently hurt or killed every year when they travel beneath semi-trailers that have missing or inadequate underride guards. Those people and their families have more immediate and urgent concerns than past or pending legislation, like how to get their lives back on track after a devastating accident.

One way might be an injury or wrongful death lawsuit. If a tractor-trailer's underride guard failed to do its job, then the responsible parties—usually the company that owns the trailer and/or the manufacturer who assembled it—may be liable for that failure. Holding them accountable can be a long and complicated process, however, and the assistance of experienced truck accident attorneys can be invaluable.

The Texas truck accident attorneys at Grossman Law Offices have decades of combined experience helping people injured in many kinds of truck accidents. If you were hurt or lost a loved one in an 18-wheeler underride accident, call Grossman Law Offices today for a free consultation.