As lawmakers press General Motors and regulators over their decade-long failure to correct a defective ignition switch, a new review of federal crash data shows that 303 people died after the air bags failed to deploy on two of the models that were recalled last month.
The review of the air bag failures, by the Friedman Research Corporation, adds to the mounting reports of problems that went unheeded before General Motors announced last month that it was recalling more than 1.6 million cars worldwide because of the defective switch. G.M. has linked 12 deaths to the defective switch in the two models analyzed, the 2003-5 Chevrolet Cobalts and 2003-7 Saturn Ions, as well as four other models.
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The analysis by Friedman Research, a company that analyzes vehicle safety data, looked at cases in which the air bags failed to deploy, but did not attempt to evaluate what caused the crashes.
The Center for Auto Safety, a private watchdog group in Washington, commissioned the study, and, in a letter to the National Highway Traffic Safety Administration, criticized the agency for not detecting the air bag failures, as well as the defective ignition switch.
"N.H.T.S.A. claims it did not do an investigation because it did not see a defect trend," Clarence Ditlow, executive director of the center, wrote in the letter. "In some instances, single complaints can trigger a recall."
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Regulators said that there was still not enough evidence to warrant an investigation.
"N.H.T.S.A. uses a variety of tools to evaluate the more than 40,000 complaints it receives each year," the agency said. "In this case, the data available to N.H.T.S.A. at the time did not contain sufficient evidence of a possible safety defect trend that would warrant the agency opening a formal investigation."
General Motors criticized the use of the database, called the Fatality Analysis Reporting System.
"As knowledgeable observers know, FARS tracks raw data," Greg Martin, a G.M. spokesman, said. "Without rigorous analysis, it is pure speculation to attempt to draw any meaningful conclusions."
G.M. has recalled six car models because of defective ignition switches that, if bumped or weighed down by a heavy key chain, can shut off engines and power systems and disable air bags. On Feb. 13, it recalled 778,000 cars, including the 2005-7 Chevrolet Cobalts and 2007 Pontiac G5. Twelve days later, the company more than doubled the recall with four more models — the 2003-7 Saturn Ion; the 2006-7 Chevrolet HHR and Pontiac Solstice; and the 2007 Saturn Sky. All of those models used the same ignition switch, and none are in production anymore.
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The company told N.H.T.S.A. that it had received reports of the ignition defect as far back as 2001, according to documents filed with the safety regulator this week. G.M. said the problem has been linked 31 accidents and 12 deaths, but the company has declined to release details of those incidents, including dates, locations and names of victims.
"Research is under way at GM and the investigation of the ignition switch recall and the impact of the defective switch is ongoing," said Mr. Martin, the G.M. spokesman. "While this is happening, we are doing what we can now to ensure our customers' safety and peace of mind. We want our customers to know that today's G.M. is committed to fixing this problem in a manner that earns their trust."
The G.M. ignition problem is connected to air bags because, to deploy, they require electrical power provided by the engine. The power is needed for a complex electronic system of sensors and a computer that consider factors ranging from how rapidly a vehicle is decelerating to how close the occupant is seated to the air bag, said David Zuby, the chief research officer for the Insurance Institute for Highway Safety, which is financed by insurance companies and conducts about 80 crash tests a year.
Then, the computer determines whether to deploy the air bag with full force or at a lower level. The goal is a balancing act to protect the occupant from the impact of the crash, while keeping the air bag itself from causing an injury.
The Center for Auto Safety's letter said that 303 front-seat occupants, where air bags are situated, had died in non-rear-impact crashes of Cobalts and Ions, in which the air bags did not deploy. That is about 26 percent of a total 1,148 fatalities — including those of back-seat occupants — that involved the same models.