The Insurance Institute for Highway Safety (IIHS) has just introduced an additional test, a frontal crash that simulates just a small overlap between the front of a car and an object or vehicle it hits.

Since 1995, the IIHS has conducted frontal-offset crashes that engage 40 percent of the car's left front, the section directly in front of the driver. The new small-overlap test involves just 25 percent of the width of the vehicle, concentrating the force on essentially the left front corner. The tested vehicles careen into a 5-foot-tall rigid barrier at 40 mph. The earlier test will be retained, along with side-impact and roof-strength tests, as part of a vehicle's overall safety score.

According to the IIHS, nearly a quarter of the fatal and serious-injury crashes that occur in vehicles rated "Good" in the current offset test involve a small-overlap impact. (See IIHS release.)

A study by the Medical College of Wisconsin found that small-overlap crashes result in an increased incidence of head, chest, spine, hip, and pelvis injury. This type of crash is common on two-lane roads with two-way traffic and no center median. Single vehicle crashes (into a tree or a pole) account for 40 percent of small-overlap crashes.

Since these crashes involve some rotating around the point of impact, the side-impact air bags are supposed to deploy, as well. If they don't deploy, the IIHS takes points off. If a door opens or seat attachments fail, the score drops to "Poor." This test can be challenging for a vehicle structure since the impact often misses the two front rail members that absorb and mitigate crash energy.

The IIHS has completed testing a group of 2012-model-year upscale sedans, and the results are mixed. The Acura TL and Volvo S60 earn Good ratings, while the Infiniti G earns an Acceptable.

The Acura TSX, BMW 3-Series, Lincoln MKZ, and Volkswagen CC earn Marginal ratings.

The Audi A4, Lexus ES 350, Lexus IS 250/350, and Mercedes-Benz C-Class earn Poor.

"Nearly every new car performs well in other frontal crash tests conducted by the Institute and the federal government, but we still see more than 10,000 deaths in frontal crashes each year," Institute President Adrian Lund says. "Small overlap crashes are a major source of these fatalities. This new test program is based on years of analyzing real-world frontal crashes and then replicating them in our crash test facility to determine how people are being seriously injured and how cars can be designed to protect them better.

The IIHS will be incorporating the results into the ratings for 2013. Vehicles that do well in this test and already boast Top Safety Pick status will add a top-tier safety designation, in addition.

Are there any cars apt to do better than others in this type of crash? Maybe. The IIHS says that Volvo started to design for this type of crash back in the early 1990s—not a surprise given the Swedish company's early adoption of several safety advances.

It also goes to show that road design plays a role in auto safety: the more center medians the better, and the fewer poles and trees near the side of the road, the better. One might also conclude that one of the latest features in some new cars today, such as lane departure warning, ought to go some way toward preventing this type of crash. We'll have to wait until enough data is amassed to see the effectiveness of this promising technology.

As manufacturers design to do well in this test, it might mean adding weight, which in turn would adversely affect fuel economy. Such trade-offs have always been the price to pay in safety engineering. But if it's a real life-saver, we believe a trivial sacrifice in fuel economy is well worth it.

Related:
Crash test videos
Guide to car safety
Smarter, safer cars