Should Truck Trailers Have Side Underride Guards?
September 23, 2019

Should Truck Trailers Have Side Underride Guards?

In 2017, the Insurance Institute for Highway Safety tested a newly developed side underride guard. - Photo courtesy AirFlow Deflector
In 2017, the Insurance Institute for Highway Safety tested a newly developed side underride guard. 

Photo courtesy AirFlow Deflector


A $42 million verdict in a tragic crash has brought attention to the question of whether trailers should have side underride guards.

In 2015, 16-year-old Riley Hein was killed on a New Mexico interstate in an underride crash. The car, stuck under the trailer, was dragged for nearly half a mile before bursting into flames.

After a two-week trial, the jury found that Utility Trailer Manufacturing and the truck driver, who was not a party in the suit, were negligent in Riley Hein’s death. The verdict assessed damages of $42 million, finding the driver 55% responsible and Utility 45% responsible, apparently for not manufacturing a trailer with side underride guards.

HDT reached out to Utility for comment on the judgment. Via e-mail, the company expressed its condolences to the Hein family for their loss and emphasized its commitment to putting safe trailers on the road.

“At times, Utility’s trailers are involved in accidents, some of which are caused by the negligent actions of drivers of the tractor or automobile,” the company stated. “Such an accident caused Riley Hein’s death in 2015 when Hein lost control of his car, hit the side of a tractor pulling a Utility trailer, bounced into the concrete jersey wall, and caromed back under the side of the trailer, where an inattentive [truck] driver dragged his car under the trailer wheels for 1/2 mile.” Both the truck driver and the teen, Utility noted, had only four months of driving experience.

Even though there was a finding of negligence, Utility pointed out that the jury “determined that Utility’s trailers were not defective, finding that they did not ‘present an unreasonable risk of injury.’

“Utility Trailer does not believe it negligently designed, tested, or manufactured its trailers. Utility Trailer presented uncontroverted evidence that adding a side-underride guard to its trailers would make the trailers more dangerous to the motoring public. Utility Trailer noted that plaintiffs’ lawyers had acted improperly throughout the trial and believe that these improprieties are reversible error and warrant a new trial. Utility Trailer is exploring its appellate options as it awaits final entry of judgment.”

Side Underride in the Media

Nevertheless, some of the media coverage of the verdict has been somewhat sensationalized.

A Washington, D.C. TV channel, WUSA9, said the “landmark court case could change the way you’re protected on the highways,” claiming that trucking industry leaders “secretly fought new features that would keep you safe even though they knew the risks.”

“Internal documents revealed the industry has been fighting the use of side guards for years,” intoned the reporter.

The station showed on screen a 2006 letter from the Truck Trailer Manufacturers Association to the National Highway Traffic Safety Administration. It appears to be a comment on a proposed rulemaking on rear underride guards, but cites an earlier NHTSA report that “combination truck side underride countermeasures have been determined not to be cost-effective.”

“The report addressed the costs and benefits of theoretical side impact guards based on the assumption that an equivalent of the current rear impact guards…. could be installed along the sides of truck trailers …. The technological feasibility of such hypothetical guards was expressly not addressed. The modifications to trailer frames, floors and side wall structures needed to provide sufficiently mounting locations for such side guards, as well as the added weight and cost of those modifications, were also not addressed.”

Utility brought up the issue of the feasibility of side underride guards in the Hein suit, noted published reports, saying that to date, “the federal government has determined that side-impact guards have not been shown to be technologically or economically feasible.”

An Aftermarket Trailer Side Underride Guard

When TTMA wrote that letter cited by the TV station (and when Riley Hein died in that crash), there were no viable trailer underride products available in this country. Now, one company says it does have such a product.

In 2017, the Insurance Institute for Highway Safety tested this product, called Angel Wing, and it is now commercially available for the aftermarket through AirFlow Deflector.

AirFlow Deflector says its Angel Wing aftermarket side-underride guard addresses some previous concerns about adding such equipment to trailers. - Photo courtesy AirFlow Deflector
AirFlow Deflector says its Angel Wing aftermarket side-underride guard addresses some previous concerns about adding such equipment to trailers. 

Photo courtesy AirFlow Deflector


IIHS crashed cars into trailers with and without side underride guards at 35 mph and found passengers are more likely to sustain fatal injuries when hitting a trailer without the guard. One test evaluated the Angel Wing side underride protection device from Airflow Deflector, while a second test was on a trailer with only a fiberglass side skirt.

AirFlow Deflector says it makes a full suite of side-underride protection devices and other aerodynamic technology products “engineered to decrease the potential for injury and death to pedestrians and cyclists, as well as to reduce the fuel consumption rates of the global freight transportation industry.”

It sells straight-truck metal-rail side guards that look similar in appearance to the ones required in Europe, as well as composite fiberglass panel systems for refuse, delivery, cement, and other urban vocational trucks.

For semi trailers, AirFlow Deflector sells the Angel Wing side-guard, designed to withstand at least a 40-mph crash.

The Angel Wing design mounts to existing trailer cross members, with no welding or specialized tools required, and the company said that it does not add any tension or stress points to the trailer. The product adds 450 to 800 pounds, depending on the configuration, and can be installed by two people in less than two hours. Galvanized steel frame construction requires little to no maintenance, the company says on its website, and it integrates with most side skirts to maintain EPA SmartWay and California Air Resources Board certification.

Its website says the company will ship  a 53-foot Angel Wing semi-trailer kit for $2,897, with free shipping. Volume pricing is available.

Perry Ponder is the person behind Angel Wing. His first job after graduating from college was with a small trailer manufacturer, and then he worked for an accident reconstruction and forensic engineering firm. Those two experiences dovetailed to prompt him to develop Angel Wing.

HDT Equipment Editor Jim Park talked to Ponder earlier this year.

When asked about fatality statistics for side underride crashes, Ponder said it’s about 200 – but there are undoubtedly more where the law enforcement official completing the accident report doesn’t categorize it as an underride, he added. And that doesn’t count severe injuries.

“The weight concerns, I understand,” he said. “My first job out of college was for a small trailer manufacturer and we would do weight audits. Even though we only produced 24 trailers a year, we would look at every single component on that trailer to see what we could shave off to save weight.”

The earlier Angel Wing prototypes weighed 1,500 pounds for a 53-foot trailer; they’re now down to 650 pounds, Ponder said, and he’s working to shave off more. He believes legislation could take the same tack as the government did for auxiliary power units and allow a weight exemption. Even if it doesn’t, he said, saving lives should be a factor in the decision to use the devices.

“There’s a trade-off for safety. I know the trailer weights have been coming down over the years at least 650 pounds, so to give a little bit back for safety, I think, is okay.”

The Cost-Benefit Analysis

Side underride guards show up from time to time in Congress. A bipartisan bill introduced in 2017, “The Stop Underrides Act of 2017,” would have required side and front guards, but it did not pass. The bill was introduced again earlier this year in both the House and the Senate. And an appropriations bill introduced this summer in the House calls for the National Highway Traffic Safety Administration to work with experts and stakeholders “to facilitate the deployment and adoption of rear and side underride protection devices.”

Few people would argue that side underride guards could save lives. And tragic stories such as that of Riley Hein can’t help but make an appealing case for them. But at what cost?

It may seem cold and calculating to put a dollar figure on a human life, but when the government evaluates the potential benefits of regulations, that’s exactly what happens – it must determine whether the benefits to society outweigh the costs. S,o the government uses a tool called the value of a statistical life, as Marketplace explored earlier this year.

In addition to the question of how much adding such guards would cost fleets if they were purchased in the aftermarket (or add to the cost of a trailer if they were designed in), and the problem of added weight and reduced payload, many regulations result in unintended consequences.

The American Trucking Associations, in a letter opposing the Stop Underrides Act, cited just such a Truck Trailer Manufacturers Association example of unintended consequences. A European trailer maker saw trailer failures due to the increased rigidity in the trailer structure from added frame supports for side underride guards, TTMA reported. The trailers were less flexible when operated over uneven road surfaces or on surfaces that produced twisting forces, which led to the trailers becoming disabled during highway use, presenting safety risks to other motorists.

TTMA also pointed out that there would be a significantly increased likelihood of high-centering of the side guards on steep changes in highway and street levels, such as elevated railroad crossings, which can result in tractor-trailers becoming stranded on railroad tracks.

Should the federal government mandate side underride guards? Some municipalities have passed rules requiring them for urban delivery trucks, but that’s not exactly the same thing as a tractor-trailer. Given the current state of what’s available for trailers, it seems a bit like putting the cart before the horse.

Should fleets pony up voluntarily for aftermarket products such as Angel Wing? That’s a business decision that once again must weigh the up-front costs vs. the potential costs of a lawsuit involving a truck, and any potential public-image benefit. Side-underride advocates are hoping that big judgments like the one in the Hein case will push that cost-benefit equation in the direction of side guards. But we’re talking about a fledgling industry here with one player that we know of. In the coming years, those calculations may change.

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