Underride Guards: NHTSA Mandate

underride guard crash outcomes
Passenger car crash with and without underride guard.

NHTSA announce mandatory underride protection for truck trailers.

“NHTSA’s priority is the safety of everyone on our roads,” said Dr. Steven Cliff, NHTSA’s Administrator. “This new rule [mandatory underride guards] will improve protection for passengers and drivers of passenger vehicles while also meeting a critical mandate from Congress under the Bipartisan Infrastructure Law.”


Crash-collisions are something that every truck operator avoids at all costs. Not only do they place unnecessary stress and danger placed on you, they also deadly to non-commercial vehicles. The NHTSA believes that mandating underride guards on all truck trailers will drastically improve the outcomes of passenger car rear impacts.

The average commercial vehicle operator has received substantially more training than most other drivers on the road. This enhanced training is necessary to operate a vehicle that weighs many times more than the cars it shares the road with. The untrained drivers you share the road with are often the greatest danger.

When a Mild Collision Turns Fatal

Distracted driving is on the rise, and rear end collisions are one of the most common results of texting and driving. When a distracted passenger car driver rear ends you at a stop light even at mild speeds, the results can be fatal without an underride guard.

Truck trailers obviously sit much higher than the average car on the road. For many cars, the floor of the trailer is at head level. When a passenger vehicle rear ends a trailer, even at relatively low speeds, the floor of the trailer can crush the roof of the car in, much like the opening picture. Obviously this situation is often fatal to the occupants.

These crashes, which are often deadly, occur when the front end of a vehicle crashes into the back of a larger vehicle, such as a large trailer or semi-trailer, and slides under that vehicle.


Underride guards help prevent this by transferring the crash energy into the car bumper rather than the roof. Most passenger vehicles are designed with safety against collisions with other cars in mind rather than a trailer. The underride guard helps make the situation much more similar to colliding with another car.

What This Means For You

The NHTSA has issued their final rule requiring rear underride protection that can withstand a collision at 35 mph. The underride guard only needs to be designed with compact and sub compact vehicles in mind. Additionally, it must provide this protection when “50 percent of the width of the passenger motor vehicle overlaps the rear of the trailer or semitrailer.”

Most operators will find that they won’t need to do much to remain in compliance. The NHTSA estimates that 94% of trailers already have compliant guards. The NHTSA estimates that equipping all trailers with compliant underride guards will cost around $7 million. Additionally, the added weight of the underride guard will increase the national fleet cost by around $5 million.

No matter what regulations are in the present or future, American Carrier Services will be here to help guide you through the red tape.

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