The latest round of small overlap front crash tests at the Insurance Institute for Highway Safety (IIHS) show the best-selling small cars are not all created equal in safety. Of the 12 models evaluated, only half earned a “good” or “acceptable” rating and qualify for the IIHS Top Safety Pick+ award.

In fact, the 2-door and 4-door models of the Honda Civic are the only small cars to earn the top rating of good in the test. IIHS evaluated the Civics earlier this year and released the results in March. The Dodge Dart, Ford Focus, Hyundai Elantra and 2014 model Scion tC earn acceptable ratings.

The Civics, Dart, Elantra, Focus and tC earn the Top Safety Pick+ award. So far, 25 models earn the top honor. The “plus” indicates good or acceptable performance in the new small overlap test. Winners must earn good ratings for occupant protection in 4 of 5 evaluations and no less than acceptable in the fifth test.

The Institute added the small overlap front test to its lineup of vehicle evaluations last year. It replicates what happens when the front corner of a vehicle strikes another vehicle or an object like a tree or a utility pole. In the test, 25 percent of a vehicle’s front end on the driver side strikes a 5-foot-tall rigid barrier at 40 mph. A 50th percentile male Hybrid III dummy is belted in the driver seat.

Significant occupant compartment intrusion contributed to the poor rating for the Nissan Sentra. The front wheel and tire were forced rearward in the test. In the 4-door Honda Civic test, the occupant compartment stayed intact, preserving survival space for the dummy.

“The small cars with marginal or poor ratings had some of the same structural and restraint system issues as other models we’ve tested,” says David Zuby, the Institute’s chief research officer. “In the worst cases safety cages collapsed, driver airbags moved sideways with unstable steering columns and the dummy’s head hit the instrument panel. Side curtain airbags didn’t deploy or didn’t provide enough forward coverage to make a difference. All of this adds up to marginal or poor protection in a small overlap crash.”

Most new vehicles are designed to do well in the federal government’s full-width front crash test and in the Institute’s moderate overlap front test, but that is no guarantee of good performance in a small overlap crash.

In many vehicles the impact at a 25 percent overlap misses the primary structures designed to manage crash energy. That increases the risk of severe damage to or collapse of the occupant compartment structure. Also, vehicles tend to rotate and slide sideways during this type of collision, and that can move the driver’s head outboard, away from the protection of the front airbag. If the dummy misses the airbag or slides off of it, the head and chest are unprotected.

A problem with safety belts and airbags was seen with the Kia Forte, the worst performer for both restraints and structure of all of the small cars evaluated. Too much belt slack and a side curtain airbag that deployed but didn’t provide enough forward coverage allowed the dummy’s head to hit the windshield pillar and instrument panel.

In contrast, both the 2-door and 4-door versions of the Civic earn good ratings for restraints and kinematics and structure. Dummy movement during the tests was well-controlled, and both cars had only minimal intrusion into the occupant compartment, so survival space for the dummy was well-maintained.

Good side curtain airbag coverage in the Elantra helped the car earn an acceptable rating, even though the safety belt allowed the dummy to move forward 11 inches. Among vehicles in which the side curtain airbags deployed, only those in the Elantra, Civics and Scion tC offered sufficient forward coverage.

“Toyota changed the airbag algorithm in the 2014 model tC so the curtain airbag would deploy in a small overlap crash. That helped boost the Scion’s rating. Without the change, the tC would have had a marginal rating for restraints and kinematics,” Zuby says.

Having six small cars qualify for the Institute’s highest safety award broadens the choices for consumers looking to buy a small car. The latest results highlight how some automakers are designing models to perform well in the demanding small overlap test. At the same time, other automakers have more work to do.

“Manufacturers need to focus on the whole package,” Zuby says. “That means a strong occupant compartment that resists the kinds of intrusion we see in a frontal crash like this, safety belts that prevent a driver from pitching too far forward and side curtain airbags to cushion a head at risk of hitting the dashboard or window frame.”

Source: IIHS