As part of its Inside the IIHS video series, the Insurance Institute for Highway Safety takes a look at what it discovered in its underride testing. It bought trailers from the eight largest trailer makers by volume in the US, loaded them with 19 tons of concrete, then crashed a 2010 Chevrolet Malibu into them at 35 miles an hour three different ways: full frontal, 50-percent offset and 30-percent offset.
Even though some of the trailer guards meant to stop a car from submarining were good for the purpose, others weren't, but even the ones that didn't perform their duty met federal regulations. The IIHS video doesn't fault trailer makers, but does suggest – graphically – that the regulations could stand to be strengthened. You can watch the video below.