Drivers have a lot to pay attention to on the road. They watch their speed , check their mirrors, and keep an eye out for sudden stops. But one detail most drivers probably haven’t given much thought to is the diamond-shaped designs on the back of trucks, even after seeing them countless times.

No, they aren’t decorations. It’s a small detail that serves an important safety purpose, especially if there’s an accident involving dangerous cargo. Learn how the holders work, what the warning signs mean, and why some appear empty.

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What Do the Diamond-Shaped Plates on the Back of Trucks Mean?

Why Do Some Trucks Have Empty Diamond-Shaped Hazmat Placard Holders?

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What Do the Diamond-Shaped Plates on the Back of Trucks Mean?

They’re called hazmat placard holders. These metal frames hold warning signs that identify certain hazardous materials a truck might be carrying. The bare diamond in the photo is simply a holder.…