The Insurance Institute for Highway Safety is constantly crashing cars -- and the automakers love it, in the hopes they earn a "Top Safety Pick."

We posted this article for publication this week:

     More than 250 motorists were killed in crashes that involved cars slamming into the back ends of trailers on large trucks in 2011, according to the Insurance Institute for Highway Safety, even though most of these semi-trailers are required to have underride guards.
Underride guards are steel bars that hang from the backs of trailers to keep the front of a passenger vehicle from sliding underneath the trailer in a crash.     

     Recent tests done by the Insurance Institute for Highway Safety show that these guards are doing a better job than in the past, but only if the full width of a car slams straight into the center of the trailer.

     However, if a car hits at the far outer edge of the trailer, then most guards fail to prevent potentially "fatal underride," the tests found.
When the truck guards bend or break all of the passenger car's structures (designed to absorb crash energy) are bypassed. The vehicle's windshield becomes the point of main impact, the airbags and seat belts can't do their jobs, and the top of the occupant compartment is destroyed.

     In the most recent crash tests, a 2010 Chevrolet Malibu hit a parked truck at 35 mph. The Malibu is an Insurance Institute Top Safety Pick and it did a good job of protecting the crash test dummy in the Institute's 40-mph moderate overlap frontal crash test. Serious injuries to a person in that type of real-world crash would be unlikely in the Malibu.

     The eight trailers used in this progressive test met both United States standards and tougher Canadian standards that the Institute says require underride guards to withstand about twice as much force.
In the first test, when the car's full width hit the center of the trailer, the guards on all eight trailers prevented underride. In that test injuries to the crash test dummy were generally low and not life-threatening.
In the second test, when 50 percent of the car's width collided with the trailer, all but one trailer passed. In the third test, when 30 percent of the car's width hit the trailer, only one passed.

     When the guards failed, head and neck injuries to the dummy were so high that a driver in a real-world crash would have been killed, according to the report.

     The bad news is that Insurance Institute research done in 2011 showed that about half of underride crashes in the real world occurred with overlaps that were 50 percent or less.

     After the Insurance Institute conducted its first round of these tests in 2010 and 2011, it petitioned the National Highway Traffic Safety administration to develop tougher standards. When releasing the results of this new test, the Insurance Institute noted that it has not received a formal response to that petition in the course of two years, although NHTSA researchers had told the organization that they were conducting research into the matter necessary to make any decision about rule making.

     Almost simultaneously with the release of the new Insurance Institute testing, NHTSA released a field analysis of fatal truck underride crashes that was done by the University of Michigan Transportation Research Institute.
In a formal statement NHTSA noted: "Moving forward, results from the field analysis, IIHS's tests, international standards and other data will be leveraged by NTHSA and may inform potential changes to existing federal safety standards -- including more stringent rear-impact guard requirements -- based on what all the data show."

     Whatever happens, the next time you are following a tractor-trailer don't tailgate -- stay far back to allow for panic stops. -- Cheryl Jensen, Motor Matters

Manufacturer Photo: To see how well the latest underride guards work, IIHS engineers put trailers from the eight largest manufacturers through a series of progressively tougher crash tests involving a 2010 Malibu. All of the trailers had underride guards that met both U.S. standards, which requires a guard to withstand a certain amount of force at various points. When the overlap was reduced to 30 percent, every trailer except one from a Canadian manufacturer failed.

Copyright, Motor Matters, 2013