A year after the Insurance Institute for Highway Safety introduced it, many automakers are still having trouble designing cars that can do well on the "small overlap" crash test.
A small overlap crash happens when just the corner of the front of a car hits something, like another car, or a tree or a pole.
That kind of a crash can bypass the "crumple zone" of the front of the car, which is meant to absorb the force of the crash, protecting the people inside the passenger compartment from death or injury.
IIHS recently tested 12 small new cars for small overlap protection; only one, the Mini Cooper Countryman, received the highest grade of "Good."
Five others, the Chevy Volt, the Ford C-Max Hybrid, the Mitsubishi Lancer, the Scion FR-S, and the Subaru BRZ, got the next highest mark of "Acceptable."
Because the Chevy Volt also offers buyers the option of a front collision warning, the Institute gave the car its Top Safety Pick Plus award.
Four cars got a "Poor" rating, including the Fiat 500-L, the Nissan Juke, the Nissan Leaf, and the Mazda 5.
The Mazda 5 was singled out by the Institute for performing the worst on the test. From the report:
The Mazda 5 shares the distinction with two other cars of being the worst-performing models the Institute has evaluated in the small overlap test. The other two are the 2014 Kia Forte, a small car, and the 2012 Prius v, a midsize hybrid. “When we tested the Mazda 5 we saw a host of structural and restraint system problems. Parts of the occupant compartment essentially buckled, allowing way too much intrusion,” Nolan says. Injury measures taken from the dummy indicate a high risk of injuries to the left thigh and left lower leg in a real-world crash this severe. The steering wheel moved to the right, and the dummy’s head barely contacted the front airbag before gliding off the left side. The safety belt allowed the dummy’s head and torso to move too far forward, so the head made contact with the left side of the dashboard. The side curtain airbag didn’t deploy at all, exposing the head to contacts with side structure and outside objects. Plus, the driver door unlatched during the test, something that shouldn’t happen and puts occupants at risk of being ejected from the vehicle.
Russ Rader, a spokesman for IIHS, says because small cars are less safe than larger vehicles, it's important for people to buy small cars that perform the best on safety tests.
The death rate for drivers of mini-cars, the smallest on the road, is 77 per million registered cars, for example.
That number drops to less than half in the midsize car category.
Midsize SUVs have a driver death rate per million registered cars of just 13.