Oh, damn! Here's David Muir. Good evening. Will you be driving down a road to ruin without even knowing it this weekend? First on "20/20," the change to something on the highway you never knew about.... See More
Oh, damn! Here's David Muir. Good evening. Will you be driving down a road to ruin without even knowing it this weekend? First on "20/20," the change to something on the highway you never knew about. Some say it killed their loved ones. Brian Ross, asking the tough questions, looking out for you. Reporter: Just after midnight on interstate 40 in North Carolina, where a guardrail meant to protect, almost killed. We need to get somebody out here quick. I'm starting to bleed to death. All right, sir. I'm trying to locate you. Reporter: The motorist hit the guardrail head-on after nodding off and was trapped in his car, bleeding out. I'm going to die. We're trying to get some help. Reporter: The long steel rail, seen in this photo from behind the driver and passenger seats, sliced through the SUV like a thick, sharp spear and then cut off his legs. I've lost my legs in a wreck. You're saying you lost both your legs, sir? Yeah. Reporter: 36-year old jay Traylor did survive, able to save his life with a makeshift tourniquet, but not his legs. In the wreck, this one was gone. Then, I had to make the choice to lose that one, too. Reporter: It wasn't supposed to happen. This test film from 15 years ago shows how a guardrail is supposed to absorb the impact, even in a head-on crash at 62 miles per hour. The truck hits what is called the end terminal, which like a sled on a rail, moves along the guardrail absorbing the impact and deflecting and spewing the rail off to the side. That's not what happened with jay Traylor. Had the guardrails done their job, I probably would've walked away just going, "Damn, I'm an idiot." Reporter: Traylor and a growing number of accident victims across the country are suing the company that makes the guardrails, Trinity industries of Texas. Among the allegations that the company tried to save a few dollars by quietly making some slight changes in the design of what's called the Trinity et-plus. This is the original five inch et-plus. And this is the modified four-inch et plus. And that makes a significant difference? It makes all the difference in the world. Reporter: This animation shows what lawyers suing Trinity say happens with the original, gliding along the rail and diverting it to the side. And what they say can happen with the modified version. The thinner terminal jams up, breaks off and the rail drives through the vehicle. The impact is the guardrail does not have the room to expand like it needs to, to save your life. Reporter: 31-year old Rebecca dryer, a single mom from Pennsylvania, says she too was a victim of the change in the guardrail design, which pierced her car and cut off her right leg. I didn't understand what happened 'cause I didn't realize that it essentially was a spear that came through my car. Reporter: Rebecca, among those now suing Trinity, became angry and upset as she looked at the photos from her accident, the first time she had seen them. I very well could have not walked away from that. Wow. That's me? Reporter: By some estimates, there are now a half million of the re-designed Trinity guardrail terminals on highways across the country. Almost every state uses them. This failed. This is a classic failure. Reporter: But Trinity never told the federal highway administration about the changes until this man came along -- josh harman, the owner of a small, competing guardrail company who became entangled in a patent lawsuit with Trinity and had access to internal documents. You looked at the highway specs submitted to the federal government? Yes, sir. Were they in there? No, none of this was disclosed. Absolutely none of this. Reporter: Trinity officials call harman a liar and an opportunist, out to make a buck by stirring up frivolous lawsuits. He says he's out to prove a rash of accidents are tied to the guardrail changes kept secret from the government. They call you a sleazy operator. Oh, I'm sure they do. If I'm crazy, it's irrelevant. It's killing people. That's the most important thing. What I am has no bearing whatsoever. The fact that I found it, let's address that. Reporter: The company says the changes harman is talking about were "Inadvertently omitted" when it submitted documents to the federal highway administration. But an internal company e-mail obtained by ABC news shows Trinity engineers actually discussed keeping the change secret. Quote, "I'm feeling that we could make this change with no announcement," unquote. So, even that one inch change should have been reported to the federal highway administration? Absolutely. You have to ask, why would they change it? What's the motivation for changing the one inch? Reporter: Harman says it is all about the bottom line, trying to increase profits at Trinity -- something the company denies. But according to the same internal Trinity e-mail, the engineers calculated that shaving off an inch would save about $2 for each end terminal. "That's $50,000 a year and $250,000 in five years by using the four-inch channel," the memo reads. That's one of the motivations. The other motivation is reusability. And these changes, no question, ruin the terminal where it's not reusable. And that means millions to them. If you have an accident, the highway department has to buy a new one? You have to buy a new one. Reporter: Trinity has turned over two sets of safety crash tests to defend itself with federal highway officials and prove its modified version performs just as well as the original. And despite the growing evidence of gruesome accidents, federal officials accepted Trinity's defense, saying its new version meets federal safety standards. Mr. Artimovich, I'm Brian Ross from ABC news. Reporter: The official who made that decision is nick artimovich, who declined to talk with us until we showed up at an industry conference earlier this week. Why did you make that decision? Based on the evidence that was presented to us. And you think they're safe now on the highways? As I've said, please talk to our office of public affairs. You can't answer that question? No. Whether they're safe? Safety is a relative matter. Reporter: Artimovich is the same official who once expressed concern "That it is hard to ignore the fatal results." But after Trinity officials asked for what they called an "Intimate" meeting with M, artimovich decided there was no problem with the new guardrail terminals. I did meet with Trinity. And do you feel they're safe? They have the met the crash testing as required. And what about the fatal accidents that you have been talking about? I'd really ask you to, to our office of public affairs. Reporter: So, the modified guardrails remained and remain on the road, including on this highway in Missouri where brad able, a father of four, ran into one earlier this year. It was a known defect. It was a defect that Trinity industries had known long before this accident in January, 2014. And when it locked up, it speared, punctured the driver side door and killed brad able. Reporter: The fact is, on a high-speed highway, any guardrail or stationary object presents a potential hazard. Trinity says the aftermath pictures of the fatal and serious accidents don't prove anything. That each accident has its own unique circumstances and that their product has a proven record of safety. Even so, federal highway officials told "20/20" this week that a nationwide review of the safety of all guardrails will soon begin. For Rebecca dryer, still dealing with the loss of her leg, not soon enough. They know what's wrong with them. Change them back, change the heads back to the ones that were safe, that weren't failing, that weren't having these problems. 'Cause how many more people do you want to lose limbs and go through all of this? So, what do you make of that? Is there something on the roads you want investigated? Tweet me and you can tweet Brian.
This transcript has been automatically generated and may not be 100% accurate.