The Chevrolet Impala and the Toyota Avalon each received a "good" rating in the Insurance Institute for Highway Safety study of eight large cars released on Sunday. "Good" is the top score in the study.
Six other large sedans tested did not fare as well.
Automakers voluntarily will make the safety feature standard on all vehicles by 2009. Nearly 10,000 people died in side-impact collisions in 2004, CBS News correspondent Joie Chen reports.
The Buick Lucerne and Hyundai Azera, both tested with optional side air bags, received an "acceptable" rating, while the Buick LaCrosse and Chrysler 300 were rated "marginal," even equipped with the optional side air bag feature.
The Chrysler 300, Ford Five Hundred and Ford Crown Victoria had "poor" ratings when tested without the side-curtain air bags. But last year, the Five Hundred received a gold medal from the institute when tested with side air bags.
Michael Kennedy, former chairman of the Ford National Dealer Council, said most customers are willing to pay $595 for a safety package that includes side-impact air bags.
"In the grand scheme of things, for a $25,000 car, that's not a lot of money to pay for safety," Kennedy, who runs four Ford dealerships in suburban Philadelphia, told the Detroit Free Press. "For safety features, customers don't balk at paying extra."
A Chrysler spokesman said the 300 has performed well in other crash tests, earning a five-star rating from the National Highway Traffic Safety Administration.
The Insurance Institute for Highway Safety said 9,700 people died in side-impact crashes in 2004 and that more drivers in passenger cars die in side accidents than in head-on crashes.
"You need side airbags," Stephen Oesch, with the Insurance Institute for Highway Safety, told CBS News. "In a side impact, you need side impact airbags to provide protection
With pressure on, consumers can expect more carmakers to start installing side airbags as standard safety features this fall, Chen says.