Be Careful Around Those Semi Trucks

Edward Niedermeyer
by Edward Niedermeyer

Another day, another way to die in a car… and this time, the IIHS blames weak safety standards for semi-truck underride guards for this mangled Malibu [ report PDF here]. The IIHS argues that

Under current certification standards, the trailer, underride guard, bolts, and welding don’t have to be tested as a whole system. That’s a big part of the problem. Some manufacturers do test guards on the trailer. We think all guards should be evaluated this way. At the least, all rear guards should be as strong as the best one we tested

But the best underride system they tested (a Wabash) still would have likely decapitated the Malibu driver in a 30% offset hit at 35 MPH. So even if government enact the stricter standards endorsed by the IIHS, you’ll still have to hit the rear of a semi truck fairly square-on in order to reap the benefits. But of the 2,200+ passenger car occupants who died in crashes with large trucks in 2009, we have no idea how many were square-on rear crashes like the one tested. And until the IIHS gets the government to regulate bumpers height, crash test-derived standards will always be less effective when they leave the lab and get into the messy real world of the American road.

Edward Niedermeyer
Edward Niedermeyer

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  • Mikey Mikey on Mar 08, 2011

    With a 53 foot tandem trailer the rear wheels will slide back. At GM we demanded that the driver slide his wheels, before we would put an 8000 lb lift truck on the trailer. However the driver had to re position his wheels before going back to the highway. I have no idea why.

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    • Toad Toad on Mar 09, 2011

      Speaking as a truck owner: Weight distribution is the answer. If most of the load weight is in the front of the cargo area the trailer tandems can be slid forward to put more weight on the (back) trailer axles, and vice versa. Highway weight restrictions dictate how much weight can be on each truck axle, and sliding the trailer axles evens out the weight. You also want weight distribution as even as possible to increase traction and prevent skidding/wheel lockup when braking. Mikey, when you were loading trailers the tandems need to slid all the way back at the dock so they do not act as a fulcrum when the loaded forklift enters the rear of the trailer. Otherwise, when it is entering the back of the trailer the weight of a heavy forklift plus the pallet it is carrying could lift the front of the trailer like it was a giant teeter-totter, causing the forklift to slide back out along with any cargo in the trailer; havoc ensues. In addition, you cannot have the ICC bumper too low or it will scrape pavement on an incline when the rear tandems are slid forward. You see these scratches in the pavement near steep railroad track inclines. This proposed rule may be a good idea, or it may not. For example, some states have different speed limits for trucks and cars because it sounds intuitively good, but every bit of research on the subject shows that the resulting "speed differentials" are more dangerous than trucks going at the speed of traffic. The bumper rule may fall into the same category. We need research, not feel good legislation/rule making. PS: I hate the jacked up 4x4's on both safety and aesthetic grounds. They handle worse than my dancing and look at least as stupid.

  • Gilles Thibault Gilles Thibault on Mar 09, 2011

    FWIW, the Canadian regulations on the strength of these back undercarriage assemblies are different and more stringent than the US ones.

  • Roger628 Roger628 on Mar 09, 2011

    Well it's better than none at all, which is the way it used to be until the death of Jayne Mansfield spurred the legislation for them in the first place. Read more about it here. Sorry can't direct link the page-Look her up in the directory if interested .

  • Krystalkid Krystalkid on Mar 10, 2011

    That under-ride guard is set at 22" from the ground to the bottom of the bumper by the Federal Government. But there are a lot of pickup trucks you can drive off the lot with bumpers higher than that. You are two times more likely to die from a post collision vehicle fire to a pickup truck (because the bullet vehicle underrode the bumper and hit the gas tank) than backing over someone with it (yet we have back up sensors) - so how about an under-ride guard for pickup trucks like these energy absorbing ones from