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Brett Emison
Brett Emison
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Did You Know… Many Semi Truck Underride Bars May Not Be Strong Enough To Protect Drivers?


I have written before about trucking accidents, and it goes without saying that accidents involving cars and semi-trucks are often devastating for the car occupants. Furthermore, it is always a major concern to me when a piece of equipment that is supposed to prevent injuries actually causes more significant injuries. I want to make it very clear that I believe underride bars are an essential piece of safety equipment. However, it is evident that they need to be made even safer in order to maximize their effectiveness in helping to save drivers’ lives.

What Happens When An Underride Bar Fails
What Happens When An Underride Guard Fails

The Insurance Institute for Highway Safety (IIHS) is also pushing for improved underride bars and is petitioning the federal government to require stronger bars on more trucks. Some of the problems the IIHS has noted are that the bars are not required on all trucks and when they are present on exempt trucks and trailers, they don’t meet the 1996 rules for strength or energy absorption. Another problem is that “Under current certification standards, the trailer, underride guard, bolts, and welding don’t have to be tested as a whole system.”

The IIHS contends that underride bar technology has not kept pace with vehicle crashworthiness. This recent study from the IIHS examines how, why and at what speed these guards fail. The report shows that truck underride bars can fail in relatively low-speed crashes leading to deadly consequences for car occupants.

"Cars’ front-end structures are designed to manage a tremendous amount of crash energy in a way that minimizes injuries for their occupants," says Adrian Lund, Institute president. "Hitting the back of a large truck is a game changer. You might be riding in a vehicle that earns top marks in frontal crash tests, but if the truck’s underride guard fails — or isn’t there at all — your chances of walking away from even a relatively low-speed crash aren’t good.

IIHC’s Lunc also noted, “"The aim [of the study] was to see if some underride guards perform better than others and to identify what crash speeds and configurations produce different types of failure… Damage to the cars in some of these tests was so devastating that it’s hard to watch the footage without wincing. If these had been real-world crashes there would be no survivors."

The study featured 2010 Chevy Malibus (which received a Five-Star Safety rating from NHTSA and a “Top Safety Pick” from IIHS) being crashed into three different semi-trailers, one of which was certified only to U.S. standards and the other two to both U.S. standards and also to more stringent Canadian standards. Dummies were decapitated in three of the six crash tests. Trailers made by Wabash National Corp., based in Lafayette, Indiana, are engineered to exceed the Canadian requirements. Trailers made by Hyundai Translead Inc., designed to meet U.S. standards alone showed the most problems. A trailer made by Vanguard National Trailer Corp. in Monon, Indiana, was also tested. It performed better than the Hyundai trailer but not as well as the one from Wabash.

If trucking companies won’t do the right thing and improve these critical safety components on their own, hopefully NHTSA will take this study into consideration and make the U.S. regulations on underride bars more stringent.

Update [11:30 a.m. CDT]

View the IIHS truck underride guard video.

(c) Copyright 2011 Brett A. Emison


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  1. Truckie D says:
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    Nice post Brett,

    They looked at trailers — did they look at container/chassis systems at all?

    Happily, the company I lease to runs Wabash trailers, as do most of the larger US trucking companies.


  2. Brett Emison says:
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    Truckie D — thanks for reading. The IIHS has linked to some source material and video at their site (http://www.iihs.org/news/rss/pr030111.html)

  3. Ron says:
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    Please….while this is a good point please know that more lives are lost by “Passenger Cars That Tow Trailers”

    Did you know that NO STANDARDS FOR A TRAILER HITCH…!!! ANYBODY CAN MAKE ONE…anybody can make a “Homemade” trailer!!!

    A police officer was just killed by a homemade trailer with no safety chains….wrong size ball and hitch!! and our government does nothing!

  4. Ron Melancon says:
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    http://www.dangeroustrailers.org what about this…?

    United States of America through the Federal Motor Vehicle Safety Standards (FMVSS) with respect to coupling requirements and manufacturers are not obliged to certify couplings. This approach is consistent with the US government’s principle of not getting involved in pre-market approval of vehicles or components.”

    Not good enough is it Ron. Your government forgets it is the people that vote them in not Acme Trailers or Ford motor company. No wonder you have a major gun problem when manufacturers have more say than the thousands of firearm victims lifes are worth.


    In 1996 the Federal Office of Road Safety reported
    that between one and five Australian road fatalities
    per year are caused by trailers separating from towing

    Complacency Can Kill!
    All couplings can accidentally uncouple. And your Country does nothing except fight you.

  5. Brett Emison says:
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    Ron — thank you for comment. I agree with you that there are serious problems with homemade trailers and trailer hitches. I have seen this problem also in my practice.

    However, the issues of inadequate underride guards and inadequate trailers and hitches are not mutually exclusive. Just because I’ve written about one issue in this post does not discount the other (or vice versa).

    These are both important issues concerning the safety of millions of drivers on the road.

    Thanks again for reading.

  6. Ron Melancon says:
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    Excellent Point and noted! Yet you don’t have companies like U Haul, Carry On Trailers, Holmes Trailers paying off the Government political leaders to put Profit over Safety!…
    Yes these companies have figured out that it is cheaper to pay a claim then to improve safety with “Passenger Cars That tow Trailers” see this..




  7. Rob says:
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    There are enough rules and regulations for trucks. What we really need is a more through driver education program for the people of the world who don’t drive trucks. They can’t understand a truck, so they fear it. If they were educated properly, then less accidents would happen. DOT bar is to keep people from following too closely from going under the trailer, how about just getting the people to stop following so close?

  8. Brett Emison says:
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    Rob — you are obviously very passionate about this issue. However, I remain confused as to why you seem to discounting the need for robust underride protection — even while I acknowledge the need for greater trailer and hitch safety in general.

    Your suggestion that the “DOT bar is to keep people from following too close from going under the trailer, how about just getting the people to stop following so close” is misleading and inaccurate.

    Are some rear-end accidents caused by someone following too close — sure. But what about a pile up accident where the person behind the semi truck gets stopped, but is hit in the rear by another vehicle driving them forward into the trailer? What about emergency avoidance maneuvers? What about phantom black ice events in the winter. There are plenty of instances where a vehicle could impact the rear of a semi trailer without any negligence or misconduct on the part of the driver.

    But what if there was some misconduct? What if they were following too close? Should that mean a death sentence? Of course not. Accidents happen. People make mistakes. Sometimes accidents are the fault of the responsible driver.

    But because we know that — if we identify a disproportionate danger — like underriding a semi trailer — it is the responsibility of the trailer manufacturer to guard against that danger. A rear-end collision in that circumstance may result in bruises or broken bones, but it shouldn’t result in decapitation from underriding the trailer.

    I appreciate your passion — thanks again for reading.

  9. Andrew says:
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    I agree with Rob about follow to closely. And it is our trucking companies that have to follow the government standard of safety, they dont build the trailers, they buy them. So go after makes them not the guy who is driving it down the road slows for what ever accident, construction zone or redlight and has an ignorant four wheeler run into the back of us. Sometimes I wish they would pull out a calculator and figure how much does 80,000 pounds or 40 tons versus there vehicle. now a truck takes 3 football fields (300 yards) at 65 mph in dry weather to stop and they run into the back of a trailer they should be held liable for being ignorant and not stopping in the short distances there car or suv are rated for. Not I or the rest of the trucking industry should held responsible for there inadequate stopping distances to the trailer. It doesnt stop on a dime.

  10. T Wade says:
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    As a OTR driver for the last 33 years I have seen the result of cars or pickups running under the rear of a semi and yes, the smaller vehicle suffers the most.
    The law requires all tractor trailers to have a ICC bar on the rear of a over the road trailer, I do not know any exceptions in the law.
    I can recall at least six fatality accidents from cars or trucks running under the rear of a trailer in the last 33 years. All of these was caused by the car or pickup driver being distracted while driving or drunk and running under the trailer. When a 80,000 lb truck is setting still and a 2000 lb vehicle hits it in the rear then something has to give and it will not be the truck.
    I have been hit 3 times in 33 years to the rear of my trailer and each time when asked by the police for the reason it was always, I failed to see this large 80000 lb truck setting in my way. What if I had be a motorcycle then I would have been dead. At 60 or 70 mph do you really think that making the rear of a trailer stronger will decrease the damage to the smaller vehicle or making a wall stronger will cause less damage if you hit it 60 to 70 mph.
    The problem is not the rear of a truck but the nut behind the steering wheel. Better education of our drivers will do more good then a stronger piece of metal on the rear of my truck. If you could see how drivers drive on our roads every day then you would think God that more are not killed for being stupid. And a lot of these stupid acts are with the family in the car. Don’t matter if you dead right or dead wrong either way your dead.