Marianne Karth lost two of her nine children in a Georgia truck accident. The tragedy inspired the her fight for safer trucking practices, like making sure all trucks in the U.S. are equipped with strong underride guards.

Underride guards are those steel bars that you see hanging from the backs of trailers to prevent passenger vehicles from sliding underneath them in crashes. “If there’s anything I can do to help prevent some other family from having to go through the same thing, then it’s worth it,” says Karth, a Rocky Mount, North Carolina resident.

Underride Guard Fails in Georgia Truck Accident Leaving Two Dead

On May 4, 2013 Karth was driving a Ford Crown Victoria on Interstate 20 in Greensboro, Georgia with her three youngest kids traveling with her. They were heading to Arlington, Texas, where the family had previously lived.

As Karth slowed while approaching an accident two miles down the Interstate, her Crown Victoria was clipped by a semi truck hauling cars. The impact spun the passenger vehicle around, eventually pushing it underneath the trailer section of a second semi truck.

Karth’s daughter AnnaLeah was pronounced dead at the scene of the truck accident. Her other daughter, Mary, sustained severe head trauma and suffered a stroke before she got to an area hospital. She died days later.

Investigators found that Karth’s vehicle was able to slide underneath the trailer section of the semi truck because the underride guard failed.

IIHS: Underride Guards Fail, Even in Low-Speed Crashes

The National Highway Traffic Safety Administration (NHTSA)—the agency that creates national standards for truck and auto equipment—has estimated that roughly 423 people in passenger vehicles die and more than 5,000 are injured annually when their vehicles collide with the rear section of semi trucks. This statistic is, perhaps, the result of weak standards for underride guards.

The Insurance Institute for Highway Safety (IIHS) has been studying the dangers of underride guards for over 30 years. According to a 2011 IIHS study, underride guards on semi trucks can fail in relatively low-speed crashes. When passenger vehicles are able to slide underneath the trailer section of a semi truck, death and/or serious injury become far more likely because the passenger vehicle’s occupant compartment is typically crushed as the truck body sheers the safety cage. The same IIHS study found that decapitation is a serious threat in underride accidents.

Tireless Advocate for Improving Truck Safety

After Karth lost her two daughters, she took to social media and created a web page in order to build awareness on the dangers of the trucking industry. She sent 11,000 petitions to U.S. transportation regulators, including Transportation Secretary Anthony Foxx, who met with Karth in September of 2013.

Transportation Secretary Foxx promised to make progress in a “short period of time” on a variety of truck safety issues, including stronger underride guard standards. In May of 2014, Karth met with the heads of the Federal Motor Carrier Safety Administration (FMCSA), the government agency that regulates trucking companies and enforces rest rules, and the NHTSA. At the time, the NHTSA was looking into options for enhancing underride guards on trailers in response to the petitions that Karth. Nonetheless, the movement to implement stricter underride guard standards seemed to drag on and on…until Karth got some good news last week.

NHTSA Endorses Stronger Underride Guards

On December 7, the NHTSA proposed a new rule to upgrade the nation’s standards for underride guards. The agency’s proposal adopts the same standards currently used by Canada, which require underride guards to provide sufficient strength and energy absorption to protect passengers of compact and subcompact cars that strike the rear of trailers at 35 miles-per-hour. The current rule in the U.S. only requires underride guards to protect at 30 miles-per-hour.

The agency has estimated that improved underride guard standards will save one life every year, and prevent between one and three serious injuries. As for the cost to the trucking industry, NHTSA officials estimate that the industry will spend roughly $13 million for trucks on U.S. roads to be in compliance with the proposed underride guard standard. An estimated 93 percent of semi trucks currently on the U.S. market already meet the standard.

The NHTSA will accept public comment on the proposal until the beginning of February, 2016. The agency will then issue a final rule on the matter.

Russ Rader, a spokesman for the IIHS called the proposal a good first step toward correcting the safety issue. But Rader added that IIHS tests show that “trailer manufacturers can go quite a bit further beyond the Canadian standard.” Additionally, Rader believes the proposal fails to adequately address truck accidents in which the impact occurs at the outer edges of underride guards, where the guards are not as strong.

The Truck Safety Coalition, which has also been at the forefront of lobbying for stricter truck safety regulation, questions whether the NHTSA has been able to tabulate the havoc caused by faulty underride guards. John Lannen, the Truck Safety Coalition’s executive director, said the NHTSA is “significantly underestimating” the benefits of improving underride guard safety.

As for Karth, she told Bloomberg News that she was glad to see this step being taken by the NHTSA. “I’m hoping everything will be done to make these guards as strong as possible,” she said, adding that “a whole lot more can be done than just meeting the Canadian standard.”