IIHS

In a flourish of safety-related messaging

, Honda has announced that the 2014 Odyssey will be the first minivan to earn a Top Safety Pick Plus (TSP+) rating from the Insurance Institute for Highway Safety (IIHS). It's a noteworthy-sounding award, but it's important to know exactly what's behind the testing and what constitutes a TSP+ rating.

IIHS is an independent, nonprofit organization funded by auto insurers. It puts U.S.-market vehicles through a battery of tests to determine various levels of safety. This is above and beyond testing done by the U.S. Government's National Highway Transportation Safety Administration (NHTSA). While IIHS doesn't have any legal authority over vehicle-design requirements, its ratings and testing carry considerable weight with both car buyers and insurers. This indirect pressure drives automakers to make sure their newest designs not only meet NHTSA testing requirements, but also perform well in IIHS tests.

Many people are familiar with the IIHS front overlap test, in which only 40 percent of the front of a car hits a solid barrier. But in 2012 the Institute unveiled its latest torture test: the small overlap frontal crash. It represents one of the most brutal crash scenarios and one of the most difficult engineering challenges. In the lab test the car impacts a rigid wall at 40 mph with just the outside 25 percent of the front bumper contacting the barrier. Translating this to the real world, think of it as one car colliding with a pole, tree, or another car, but making contact only at roughly the center line of the headlight. Passing this test, along with all of the existing IIHS tests, constitutes exemplary performance denoted by a TSP+ rating. Here's the Odyssey's test:

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Over the last 40 years automakers have spent considerable effort in developing and optimizing the crumple zone concept, wherein the front bumper and frame rails collapse during a crash and absorb the forces. What makes the small overlap crash so challenging is it bypasses the primary crumple zone structure, concentrating force in the front suspension, at the firewall, and at the base of the A-pillar—areas not traditionally designed to absorb and dissipate crash forces.

Manufacturers that had the good fortune of their programs align with the announcement of this test have factored in its requirements and modified their designs already, whereas older platforms have not. This is illustrated to great effect in the below video.

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On cars that fail the test, wheels push backward into the footwell or door sills, and A-pillars buckle into the driver's space. Doors and door skins can rip away, and pedal boxes push up toward the driver. These failures result in serious crushing injuries to the lower legs and hip area. Perhaps the most dangerous failure is when the cross-car dash beam bends inward, forcing the steering wheel—and by extension, the airbag—out of position. This last element has doubly negative effects when combined with the motion of the driver's body in this type of accident. The head and chest move forward and outward toward the A-pillar, which can easily cause the driver's head to slip right off the side of the airbag and strike the dashboard.

There are two schools of thought on how to improve performance in this test. The first is to extend the bumper and crumple zones outward and design the suspension to absorb loads and then break away to the outside of the car. Combined with a cabin structure that's strengthened to resist any intrusion or bending, this re-creates the traditional crumple zone concept. The other idea is to deflect the crash forces away from the car by using the frame and suspension as a wedge, avoiding absorption of much of that kinetic energy. Honda's Accord and Civic use the former method, whereas the Jeep Wrangler uses the latter. Which will be the preferred method across the industry remains to be seen.

What's interesting, and perhaps troubling, about this crash scenario is that it doesn't translate perfectly to real-world head-on vehicle crashes. The test's static barrier doesn't move nor does it deform, and so the way this type of accident happens in real life is significantly different than what is seen in the lab. Honda's chief engineer for safety, Chuck Thomas, says, "You can design for the test, but that's not necessarily the most successful in the real-world accident. There are components ripping and breaking and getting caught on each other and that's almost impossible to simulate. Although the test is a good one, we like to focus on how the cars perform in the real world."

Over the next few years it's certain that automakers will spend a considerable amount of time and money to adapt to this new test. For example, Toyota's CEO Osama Nagata has announced the company's next round of midcycle refreshes will include significant structural improvements to counter the poor performance of many of the company's cars. In the end, all vehicles will be even safer than they are today because of this new test, and that's the kind of thing that's hard to complain about.

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