Well-built guards can prevent smaller passenger vehicles from sliding beneath the sides of semitrailers, causing potentially serious or fatal collisions, according to a new crash test report released Wednesday by the Insurance Institute for Highway Safety.

IIHS ran two 35-mph crash tests – one with a side underride protection device from Airflow Deflector Inc. called an AngelWing, and the other with a side skirt made of fiberglass that is meant to improve aerodynamics, not prevent side underride.

When the test vehicle struck the side of the 53-foot-long big rig with the AngelWing side guard, the panel bent, but stopped the passenger car from sliding underneath. Upon impact, the test car that hit the truck equipped with only the fiberglass side skirt did not stop and became lodged underneath the trailer after it sheared off part of the roof.

“Our tests and research show that side underride guards have the potential to save lives,” said David Zuby, executive vice president and chief research officer for IIHS. “We think a mandate for side underride guards on large trucks has merit, especially as crash deaths continue to rise on our roads.”

Only 28 percent of a 53-foot trailer’s length would be protected from underride without a side guard, Zuby said.

With a side underride guard in place, 62 percent of the trailer’s length would be protected, he said.

According to the U.S. Department of Transportation, approximately 4,000 people have been killed in collisions involving underride between 1994 and 2014. Of that number, around 1,530 were related to side underride crashes.

Marianne Karth knows firsthand the devastation caused by an underride crash involving a tractor-trailer.

Karth’s teenage daughters AnnaLeah and Mary died from injuries sustained in a May 2013 rear underride crash. Karth’s Ford Crown Victoria was hit by a truck, spun, hit again and shoved backwards under another semi-trailer, flattening the rear compartment where her children were sitting.

Since their deaths, Karth has been advocating for legislative and regulatory reform that would mandate side underride guards and strengthen existing rear underride guard standards, which are mandatory, on semitrailers.

In 2009, IIHS began a study focused on underride guards that met the National Highway Traffic Safety Administration standards first formulated in the 1980s. That regulation is still in place and determines what types of trucks need underride guards and defines their characteristics, including clearance to the ground and strength.

angel wing underride guard test

Crash test with a side underride protection device from Airflow Deflector Inc. called an AngelWing. (Photo: IIHS)

In 2015, NHTSA announced a new proposal stating that it would adopt the more stringent standards that Canada has in place, but the agency has yet to move forward with it.

“It’s frustrating to know that our tragedy could have been prevented,” Karth told Trucks.com.

Karth and another mother, Lois Durso, have drafted legislation aimed at preventing underride crashes, called the Roya, AnnaLeah and Mary Comprehensive Underride Protection Act of 2017. Durso lost her 26-year-old daughter, Roya Sadigh, in a side underride crash 12 years ago.

This is the first time IIHS has evaluated a side underride guard, but has been testing rear underride guards for several years.

Some trailer manufacturers are taking notice and voluntarily making improvements to curb serious or fatal rear underride crashes.

In March, the IIHS recognized five North American semitrailer manufacturers as winners of its new Toughguard award. The acknowledgement is based on equipment submitted by the trailer makers, which withstood rear underride guard testing meant to replicate real-life-crashes between a passenger car and a semitrailer.

Manufacturers that received the accolade include Great Dane, Manac Inc., Stoughton Trailers LLC, Vanguard National Trailer Corp. and Wabash National Corp.

Saint-Georges-de-Beauce, Québec-based Manac Inc. recognizes that the Canadian design requirements for underride guards are tougher than in the U.S.

“We take a different approach with the underride guard because under Canadian regulations, it must withstand about twice as much force as required by the U.S. rule at the point where it attaches to its vertical support,” said Charles Dutil, Manac's president. “The supports of the Manac underride guard are bolted to a reinforced floor and spaced just 18 inches from the edge.”

In Europe, side and rear underride guards have been required on trailers since 1989.

The Truck Trailer Manufacturers Association opposes mandating side underride guards on trailers, stating they are not cost effective and may add weight, which could weaken them.

Until side underride guards are mandatory and stricter rules are adopted to strengthen rear underride guards, Karth said she will continue her fight.

“I am convinced stronger rear underride and mandatory side underride guards will save lives, that’s what gives me the strength continue,” Karth said. “I will not compromise on this issue because too many people have died already and we can’t compromise any longer.”

Related: When Will We Tackle Underride? – The Hidden Dangers in Trucks

About The Author

Clarissa Hawes

Clarissa Hawes is a Trucks.com staff writer who covers trucking and freight. She is an award-winning journalist with over 10 years of experience covering the trucking industry. She can be found on Twitter: @cage_writer.

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