Don’t Rear-End a Tractor Trailer, Or You Will Die

The Insurance Institute for Highway Safety, the insurance industry-funded research organization (which, due to its nature, has an obvious interest in reducing injuries and vehicle damage in crashes and/or preventing crashes in the first place) puts out some interesting research-related press releases from time to time.   shows that there is a substantial risk of decapitation if a motorist in a normal car has a rear-end collision with a tractor trailer.

The guards at the rear of trailers, called ICC bumpers (named for the Interstate Commerce Commission) have been required since 1953, and are intended to prevent a phenomenon known as “underriding” – which is when the car collides with the trailer and goes under it, leaving the windshield, A-pillars, and unfortunately the front-seat occupants to stop the car’s momentum in an accident.

ICC bumpers were basically unchanged from 1953 until 1998, when a 1991 NHTSA rule on a more robust design went into effect.  However, the older trailers were not required to have a retrofitted bumper, so they are permitted to continue with the older, less-safe design until they are retired.

In a car-trailer collision, the problem of underriding is not as severe if the car’s full width hits the trailer.  But in situations where there is less-than-perfect alignment between the car and the trailer, the trailer’s bumper often breaks off, or otherwise is not strong enough to support the substantial crash forces coming from a car.

In IIHS tests, a 2010 Chevrolet Malibu faced off against eight common trailers.  The trailers were built by Great Dane, Manac, Hyundai, Stoughton, Strick, Utility, Vanguard and Wabash.  The IIHS regards as a Top Safety Pick, and in the insitutute’s normal crash-test procedures, does a good job of protecting occupants.

That turned out to be true as well in a 35 MPH car-to-trailer crash, where the bumpers in all eight trailers prevented Malibu occupants from likely serious injuries as long as the car’s full width hit the trailer.  But when only 50 percent of the car’s width hit the trailer, the story was different.  In those scenarios, all but one trailer passed the test (the Vanguard trailer failed).  In a third scenario, when only 30 percent of the car’s width hit the trailer (meaning both 30 percent of the car and 30 percent of the trailer each had to absorb 100 percent of the crash’s full force, only one trailer passed (the Manac trailer was the only one to pass the toughest test).

By “not passing,” we mean that head and neck injuries were so severe that the driver would most likely have died from the crash.

Canada requires stronger bumpers in trailers than the U.S. does (Canada’s rules require that trailer bumpers be twice as strong as the U.S. standard.  Still, even the Canadian standard is not enough.  Basically, the way to improve the guards it to move the vertical supports closer to the outside edges of the trailer, rather than in the center as most of them are now.

In the real world, about half of all car crashes into trailers have a 50 percent or less overlap, meaning that there’s about a 50-50 chance of a deadly collision.  Car-to-trailer underriding crashes kill about 250 people per year.

Unfortunately, it’s not just rear-end collisions with trailers that can kill car drivers.  A car hitting the middle of a trailer, where there’s typically no bumper or guard, has the same deadly effects, if not worse.  Technology exists to mitigate the risk in those types of collisions as well.  In fact, about half of the annual fatalities .

It’s probably worth me mentioning at this point that after reading about this and seeing the crash-test videos that I feel even more fortunate that my wife and son are still alive.  You see, earlier this year, a tractor trailer barreling down the road had to slam on its brakes, and the trailer crossed the center line and slammed into the 2008 Toyota Sienna carrying my wife and son.  The A-pillar on that demolished van bears a nasty scar where the underside of the trailer hit it.  To this day, my wife refuses to allow our children to ride in any vehicle smaller than a minivan because of what might have happened in a smaller, less-safe vehicle.

For its part, the IIHS petitioned the NHTSA in 2011 to require stronger underride guards and to require them on more trucks whose size and shape is otherwise incompatible with passenger-car crashes.  NHTSA has not changed the rule, but said that it is studying all fatalities in an effort to recommend future rule changes to further reduce highway fatalities.

Author: Chris Haak

Chris is Autosavant's Managing Editor. He has a lifelong love of everything automotive, having grown up as the son of a car dealer. A married father of two sons, Chris is also in the process of indoctrinating them into the world of cars and trucks.

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  1. This article may increase my fear of tractor trailers even higher than it was, but it is something everyone should consider when driving. A tractor trailer cannot do any act as fast as your car can, stay back from their rear, do not ride next to them and always know where they are. ANY vehicle combined with the force and weight of a tractor trailer is going to be a bad combination 🙁 I am lucky, as Chris mentioned above, to be OK after a trailer jack-knifed into my poor van 🙁

  2. According to the rear end collision data from the Swedish insurance company Folksam and Autoliv 56% of all rear-end crashes are full overlap and 28% of rear-end collisions have 1/3 to 2/3 overlap. Only 14.2% of rear end collisions would be less then 1/3 overlap and end up hitting the outside edge of this under-ride guard as shown in the video. So at least you have statistics on your side. You can also get an impact attenuator / under-ride guard for your pickup truck or SUV at

  3. Im a truck driver for 18 years. As far as rear end goes. Teach stupid people they are responseable for their own actions. Not what kind of bumper i have. Grow up. If you rear end me, dead or alive, im going to the Chiropractor for 8 mons. You will pay me $3000 a week loss wages, fix my trailer and oh yeah the whole trailer has tobe painted for the paint to match, so go ahead and blame us because you were tail gating.

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