By on May 16, 2017

under-ride crash test

In National Lampoon’s Christmas Vacation, Clark W. Griswold road rages his Ford Taurus station wagon under a logging truck to comedic effect. However, without the benefit of movie magic, the following sequence of that film should have been a joint funeral for the entire family. Crash tests conducted by the Insurance Institute for Highway Safety prove that underride accidents are as devastating as they look, and the IIHS is demanding the implementation of every safety solution available.

While tractor-trailers are legally obligated to affix underride guards to the rear of their vehicles, the same can’t be said for their flanks. Unsurprisingly, there are more passenger fatalities stemming from incidents where a vehicle strikes the side of tractor-trailer than those where it impacts the rear. Since rear underride guards have proven successful in the lab and on the highways, isn’t it time we utilized similar countermeasures for a truck’s haunches? 

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

An IIHS study from 2012 determined strong side underride guards have the potential to reduce injury risk in about 75 percent of large truck side impacts — which almost universally result in severe physical harm or fatalities among passenger vehicle occupants. This proportion increased to almost 90 percent when restricted to crashes with semi trailers.


Additional testing conducted this spring, where the IIHS evaluated a side-specific underride guard, highlighted those assertions with some brutal video footage. The Institute ran two crash tests at 35 mph — one with an AngelWing side protection system from Airflow Deflector and a second with a fiberglass side skirt designed solely to improve aerodynamics.

“In both tests, a midsize car struck the center of a 53-foot-long dry van trailer. In the AngelWing test, the under-ride guard bent but didn’t allow the car to go underneath the trailer, so the car’s airbags and safety belt could properly restrain the test dummy in the driver seat,” reported the IIHS. “In the second test with no under-ride guard for protection, the car ran into the trailer and kept going. The impact sheared off part of the roof, and the sedan became wedged beneath the trailer. In a real-world crash like this, any occupants in the car would likely sustain fatal injuries.”

It may not be the single greatest threat facing today’s motorists, but it’s doubtful anyone would be opposed to the IIHS encouraging the usage of well-built side guards on oversized trucks.

[Images: IIHS]

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38 Comments on “IIHS Pressing for Countermeasures Against Horrific Underride Scenarios...”

  • avatar

    I can see why this would be a good idea, but I’m not sure the trucking industry would be willing to pay the weight penalty, the IIHS can’t force action, and the current crop of Feds are 100% unlikely to do anything.

    • 0 avatar

      How many people are hurt or killed every year from this type of accident? What would be the cost of retrofitting every semi trailer? My guess it would cost many millions of dollars for every life saved. There are better ways to spend that money and save more lives. I’d venture to guess distracted driving kills and injures far more people each year.

      • 0 avatar

        Good thing the IIHS doesn’t operate on guesswork.

        • 0 avatar

          Well, they also don’t work with numbers regarding the amount of weight added to each vehicle, the consequent amount of extra fuel burned and carbon dioxide added to the atmosphere. This is why we have to systemically evaluate regulations like this, rather than let the “for the children” make all the decisions. There are cretins who think “if it saves just one life” is a legitimate argument. Nowhere in this article do I see the actual number of side impacts to trailers. Maybe we should ask why people are driving into the sides of trailers. Are the currently regulated reflectors and side markers up to par?

          • 0 avatar

            Yeah, IIHS can tell us number of incidents and probable reduction.

            It can’t – and doesn’t try to – tell us the cost/benefit analysis at any level.

          • 0 avatar

            They certainly can make projections. They could start with the number of people killed this way. How many is it?

          • 0 avatar

            “In 2015, 301 of the 1,542 passenger vehicle occupants killed in two-vehicle crashes with a tractor-trailer died when their vehicles struck the side of a tractor-trailer. This compares with the 292 people who died when their passenger vehicles struck the rear of a tractor-trailer. Because of gaps in federal crash data, IIHS researchers can’t determine exactly how many of these crashes involve underride, but they estimate that underride occurs in about half of fatal crashes between large trucks and passenger vehicles.”

      • 0 avatar
        Joe K

        I agree, there are other ways people needlessly die in the US every year but they are ignoring, why pick on this rare occurrence?

  • avatar

    I never understood why any vehicle with no off-road pretenses should have anywhere near the vertical space found under a typical semi trailer. The issue is that cars will travel through empty space (or fiberglass) but not occupied space (by the trailer frame/body, or under-ride guard). If that space needs to get occupied for safety reasons, why not have it store (smaller) cargo while they’re at it? Take those under-ride guards and design them to be a crashworthy frame for some storage bins. Better aero, better safety, and some utility to boot. You lose the crazy breakover angle but again… who’s rock-crawling a 36-wheeler?

    • 0 avatar

      Ever cross a railroad track?

      Ever do it in a vehicle with some 400+ inches between your axles?

      Ever seen what happens to an object that gets beached on railroad tracks?

    • 0 avatar

      In the rural part of Ohio where I grew up it was popular for semi drivers to skirt construction etc by simply doing their own little detour cross country (regardless of what the actual detour was). It was fast and easy for the driver because all our our roads ran north/south and east/west – and the area had low population density.

      Complicating matters was the high number of unlighted, un-gated railroad crossings. Even with insane breakover angles there was at least one semi trailer that managed to get “hung up” on a small rural crossing near my house because it was simply too steep.

    • 0 avatar

      Do you…..know what a container looks like and how they are stacked?

    • 0 avatar

      Ease of loading as well as type of load dictates the shape of a trailer. Freight trailers need to be loaded and unloaded quickly to reduce down time. The only trailers that are lower to the ground are almost always loose bulk carriers primarily for wood chips or similar loose aggregate. Even with that being said, gravel trailers tend to have flat floors. Belly dumps, as the name implies unload from the bottom but are rather limited in use. Most logging trailers have nothing between the axles other than the reach. Low beds are typically for loading machinery.
      You have to realize that in many respects that 45-54 foot span isn’t much different than that of a bridge deck. It needs to be able to flex and deform with load. You add barriers strong enough to repel vehicle incursions and you affect the overall structure’s ability to flex.

      It isn’t as simple as just filling in a gap.

      • 0 avatar

        Just weld vertical HSSs to the bottom of the trailer and run horizontal HSSs between them with bolts in long-slotted holes to allow for the trailer moving and expanding/contracting.

    • 0 avatar

      Did you see the pix of “The Beast” getting hung up in London? That’s why. Whatever else their faults may be, semis are long and have a ridiculous breakover so they have to be fairly high. Wait, that sounds like a fault too.

  • avatar

    As said the merits exist, but the cost would probably make it unfeasable. The structure would have to be capable of hinging upwards to prevent the long trailers from becoming high centered. The structures would add weight, hurting the fuel economy of already emission-laden tractors. Would hurt the existing aerodynamic packages being used since they wouldn’t be able to be added to the walls without significant damage from high centering.

    Money is better spent educating drivers about safety or/and proper car maintence. Not only would that decrease these accidents but it would decrease other accidents as well.

  • avatar

    I remember Nightline, or 60 Minutes, or Dateline covering this very issue at least 20 years ago, and comparing to US to European standards. They also covered the lack of mandated reflectors (at the time) for the side of semi-trailers so that would be visible at night if all lights were turned off.

    They can push all they want, the current administration is not going to add cost to trucking companies for this change.

  • avatar

    I’d much rather see the IIHS go after the woefully inadequate seatback strength requirements since legislators and automakers have been kicking that can down the road since the 1970s with almost no meaningful improvements. The fact that your car seat is virtually guaranteed to collapse in a rear-end collision over 35 or so MPH is nauseating, especially when you see what it does to the people in it (paralysis and/or death) and the small children frequently placed behind those seats (death or severe brain trauma). Really the only car companies who do well in seatback strength are BMW, Mercedes, and of course, Volvo.

    I’m glad I don’t have any kids to ride in my back seat but ever since I found out about how ridiculous the strength requirements are (an office chair can exceed the standard), I’m a bit more cautious about watching my tail when slowing down. Hyundai couldn’t measure the MPG properly on my Elantra so I have no expectations that the seat will remain upright should I be rear-ended by some soccer mom texting in a Tahoe.

    My point is the IIHS has encouraged car companies to improve safety where government agencies failed by using negative press against them so my hope is they could do the same with seats.

    • 0 avatar

      The IIHS already conducts rear crash stimulation tests with seats on a sled with a dummy riding in the seat.

      “The sled test replicates the forces in a stationary vehicle that’s rear-ended by another vehicle of the same weight going 20 mph, which accelerates the struck vehicle to 10 mph.”

      The IIHS has never reported a physical seatback failure in its testing.

      Also note that the NHSTA is probably slow-moving on this issue because:

      a) It’s government work

      b) The relationship between seatback strength, whiplash protection, and overall occupant protection is murky, with some sources saying that seatbacks needs to be strengthened, but others arguing that stiffer seatbacks can lead to increased whiplash injury. Better legislate it right the first time than to have to change it down the road because of increased injuries/unforeseen problems, I guess.

      • 0 avatar

        You do realize that this very web site did a story nearly a year ago chronicling seat back failures and that they’d killed 100 people right?

      • 0 avatar

        A 20mph test is fairly weak, really. My car was rear-ended by a car traveling probably 40mph faster than mine, and the seatback collapsed under me. (My car was a 1990 Ford Thunderbird, the striking vehicle was a similar year Chevy Cavalier.) I had a neck strain, but fortunately nothing worse. And there was nobody in the seat behind me. If there had been a child in the rear seat, an injury would have been likely.

        I think the point of Andrew’s comment is that rear impact between similar size vehicles is probably much more common than T-bone side impacts between small vehicles and tractor trailers. So why did IIHS bring this up instead of tougher seat back tests?

  • avatar

    Side guards won’t happen because of the length of the trailers. They would get hung up each and every day on something or other.

    I suppose people need to drive more carefully – that is put the devices down and watch the roads.

    I know that’s an easy thing to say, but I can’t think of any other remedy.

    • 0 avatar

      I think maybe I agree. My initial reaction to this is: “how badly do you have to screw up to run under the side of a tractor trailer?” IOW, how many “one one thousands” do you have to count before the rig is in position to run under the trailer? Obviously there are exceptions like icy roads, but we can’t legislate against every potential injury.

      Not to get off topic, but the ironic thing is that the Darwinists are also the ones generally in favor of legislating against unlikely injuries typically caused by innattention. Go figure. ;)

  • avatar

    Some trailers would need to be totally redesigned to mount such guards, and at very high expense. This is the sort of rule that might be applied to new trailers – with an appropriate lead time for new designs. Requiring retrofits is not reasonable.

  • avatar

    My father’s coworker met an untimely demise in this way. A semi trailer simply switched lanes overtop (!)of his MG MGB and then he was crushed by the wheels.

    Lesson: don’t drive your MG on the highway.

    • 0 avatar

      My rule for driving a Miata: Don’t dawdle next to anything with tires taller than the car’s beltline, whether it’s a semi or a Tahoe. Either pass it quickly, or fall back.

    • 0 avatar

      Well, “crushed by the wheels” isn’t quite the accident mode the IIHS is talking about here, which is “T-boning the trailer”.

  • avatar

    Side underride protection has been the law in Europe since 1989, so the technology is already there and no major development costs need to be made.

    Beside car crashes, they also protect bike riders in the truck’s blind spot by knocking them out of the way instead of running them over with the trailer’s wheels. There’s also benefits to aerodynamics.

    I’m not for big government but this seems like a very minor investment to make for a real safety improvement.

    • 0 avatar

      How do they keep from being stuck on railroad crossings?

      • 0 avatar

        Most likely road design.

        If we weren’t as lazy when it comes to building roads, we wouldn’t have an issue with vehicles getting hung up.

        There’s no reason you can’t build a crossing that allows for long wheelbase/low slung vehicles to pass without getting hung up.

  • avatar

    Hey Malibu, how’s it feel to be playing the role of the 1959 Chevy?

  • avatar

    Well I guess with the switch from mid sized cars, this might be a little bit less of an issue for a lot of people ( where is the IIHS’s test of a Pickup t-boning a semi trailer? What is the result of this better or worse for the occupants? )

  • avatar

    Don’t drive under trailers. Problem solved.

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