Among the most recent group of 12 small cars to undergo the Insurance Institute for Highway Safety's small-overlap frontal crash test, only the Mini Cooper Countryman earned the highest rating of Good.
Pulling in the next highest rating, Acceptable, were the plug-in hybrid Chevrolet Volt, the Ford C-Max Hybrid, the Mitsubishi Lancer and the Scion FR-S and Subaru BRZ twins (models built after December 2013). The Hyundai Veloster and the Scion xB (models built after February 2014) earned a Marginal rating. The vehicles that received the lowest rating, Poor, were the Fiat 500L, the Nissan Juke, the Nissan Leaf and the Mazda 5. (All but one of the vehicles tested were 2014 models; the FR-S was a 2015.)
The small overlap evaluation, which I.I.H.S., an insurance industry-financed organization, added to its repertory of crash tests in 2012, replicates what happens when the front driver's side corner of a vehicle collides with another vehicle, or with an object like a tree or utility pole, at 40 miles per hour. This is the second group of small cars subjected to the test by the institute, bringing the total number run through the small overlap front crash test to 32. Of those, 19 earned Good or Acceptable ratings, and 13 received Marginal or Poor ratings.
The institute says it is especially difficult to get a good rating in this crash test because the impact bypasses most vehicles' front-end crash-absorbing structure, making it hard for a vehicle to absorb crash energy before it reaches the passeng er compartment. As a result, the compartment can collapse in a crash. When that happens, the instrument panel, parking brake pedal and steering column can intrude into the driver's space. When unstable steering columns are pushed sideways and seats are knocked out of position, it allows the crash-test dummy's head to miss the protection of the front air bag in the steering column and possibly to hit the instrument panel or other structures inside or outside of the vehicle.
A collapsing passenger compartment was the major issue with the four small cars that received an overall rating of Poor, Joe Nolan, the institute's senior vice president for vehicle research, said in a telephone interview. The Fiat 500L, Mazda 5, Nissan Juke and Leaf received a separate rating of Poor for their structures as well.
During the test, everything in the Mini Cooper Countryman worked reasonably well, but in the Mazda 5 just about everything went wrong.
"The structure collapsed pretty dramatically, the door unhinged, the side curtain air bags didn't deploy," Mr. Nolan said, adding that the dummy's head barely contacted the front air bag before it slid off and hit the instrument panel. High crash forces on the crash dummy's leg indicated a high risk of injuries to the left thigh and left lower leg in a crash of that severity.
"I cannot think of many positives to say about the Mazda 5," he said.
In the alternat ive fuels segment, the passenger compartment of the plug-in hybrid Volt held up "reasonably well" in the test, and injury measurements taken from the dummy indicated a "low risk of any significant injuries" to a person involved in a similar crash, according to the report. In the all-electric Leaf, however, the instrument panel, parking brake pedal and footwell intruded as much as 16 inches into the driver's lower space, which meant that injuries to the left knee and left lower leg would have been likely in an actual crash of that severity.
Even though the Leaf didn't perform well in the test, Mr. Nolan said that the lithium-ion batteries in the Volt and the Leaf seemed to be in good shape after the crash, an important point since there have been concerns around the crash safety of the Tesla Model S and other electric vehicles. He said that many people ask the institute about the safety of the batteries in electric vehicles during crashes.
"We monitor the temperatures of the batteries after the crashes are done," he said. "It has been some time since the tests, and there have been no issues."
The Volt was tested on June 10 and the Leaf on June 12.
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