It's the difference of just one inch. In 2005, the guardrail manufacturer Trinity Industries shaved that much off its guardrail design, saving the company $2 per guardrail head. It also neglected to report this design change to the Federal Highway Administration. Tens of thousands of these potentially deadly guardrail heads are now installed all over the country, and after numerous accidents and deaths, states are finally banning it.

Last week, a jury found Trinity Industries had defrauded the Federal Highway Administration by failing to report the design change. In all, lawsuits have linked Trinity's guardrail to 14 accidents and 5 deaths. Fourteen states have now banned this guardrail, reports the New York Times. Among them, Virginia going one step further and even ripping out all of its Trinity guardrails.

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How can one inch make such a difference? It helps to understand how rail heads, or the ends of the guardrails, are designed to protect drivers. The rail head is a flat plate of metal that slides along a channel on the rail upon impact, pushing the metal of the rail itself out of the way. The channel on Trinity guardrail is one inch narrower, which makes it more likely to get stuck, according to some state officials. In that case, the guardrail spears right through the car.

You can see how guardrails are supposed to work (top) and do not work (below) in these gifs from an ABC News story.

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We speed past guardrails on the highway all the time, and "guardrail head design" might sound like one of the most boring subjects on Earth. But in fact, these objects are very deliberately designed and tested—well, at least they're supposed to be. A subtle design change could be the difference between life and death. [New York Times]

Top image: Lily 81/shutterstock

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