Only one vehicle tested, the 2009 Chrysler PT Cruiser, received the lowest mark of poor in side protection and rear protection.
Two other 2009 small cars, the Ford Focus and the Chevrolet HHR, got top marks in front-end tests and received the second-highest score of acceptable in side protection.
"Automakers have made big improvements to small cars to better protect people in frontal crashes," said Joe Nolan, an Institute senior vice president. "They've also added stronger structures and standard head-protecting side air bags to help in side crashes, which are tougher on smaller, lighter cars."
Sales of the entire U.S. vehicle market have declined by more than 16 percent through the end of November, according to Autodata Corp. But sales of small cars have increased more than 1 percent over the year as gas prices surpassed $4 per gallon and then fell by more than half. Small cars have grabbed a larger share of the domestic market this year, accounting for more than a third of new vehicle sales.
Nolan noted that 11 of the 21 current small cars rated by the Insurance Institute earned top scores in side protection. Only two years ago, he said, three of 19 vehicle models earned the top score.
He cautioned that no car can overcome the laws of physics - smaller cars typically provide less crash protection than larger, heavier vehicles. But the improvements in the small cars have been attributed to the growing installation of side air bags as standard equipment instead of making it an option for car buyers.
Among other new cars tested, the 2009 Hyundai Elantra and 2009 Saturn Astra received the top score of good in front-end tests and the second-lowest rating of marginal in side testing.
GM spokeswoman Carolyn Markey said the Saturn Astra and Chevrolet HHR both performed well in the government's crash tests and the vehicles "meet or exceed all federal safety standards."
During tests on the Chrysler PT Cruiser, the institute found that measurements on the driver dummy showed rib fractures and internal organ injuries would have been likely in a similar crash. Test results showed the rear passenger could have suffered serious neck injuries and a fractured pelvis in a similar accident.
"The PT Cruiser doesn't offer the same crash protection level as other small cars," Nolan said.
Chrysler said in a statement that the vehicle has performed well in government tests and the PT Cruiser is equipped with standard front and side air bags. Chrysler said a vehicle's overall safety performance can't be determined by a single test and the IIHS results are reviewed by the company to make improvements.
"Our priority continues to be designing vehicles that perform safely for our customers and their families in everyday driving conditions," Chrysler said.
The institute also recommends car buyers find vehicles with anti-rollover technology called electronic stability control. Among the vehicles tested, ESC is standard equipment on the HHR and the Vibe and it's offered as an option on the SX4, Matrix, Focus, Elantra and Astra. Stability control is not available on the PT Cruiser.
"Cars aren't involved in rollovers as often as SUVs and pickups, but when they do roll the consequences can be deadly," Nolan said.
On the Net: Insurance Institute for Highway Safety: http://www.iihs.org/
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