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In at least one Toyota crash linked to sudden acceleration, there's new evidence that the driver never applied the brakes. The March 9th accident involved a New York woman pulling out of a driveway.

NPR's Alex Spiegel reports this is not the first time federal officials have blamed driver error when a car accelerates.

ALEX SPIEGEL: In the mid-1980s, the car company Audi had a problem. Some customers were reporting a mysterious defect. Their cars, they said, were uncontrollably surging forward. There had been accidents, deaths.

Audi denied the car was the problem, so the U.S. government undertook this enormous study of sudden acceleration. And Joan Claybrook, former head of the advocacy group Public Citizen, says the report's conclusion was clear: People, not cars, were the problem.

Ms. JOAN CLAYBROOK (Former President, Public Citizen): The report was issued in 1989 by the National Highway Traffic Safety Administration. And it did conclude that this is primarily a driver error problem.

SPIEGEL: And so for 30 years, she says, when potential cases of sudden acceleration came up, it was just assumed that the people had panicked and pressed the wrong pedal.

POST-BROADCAST CORRECTION: The family members in Mark Saylor's car were his wife, child and brother-in-law. Saylor's brother-in-law made the phone call to 911.

But then, in August of 2009, an off-duty police officer named Mark Saylor got into his car with his wife and family.

Unidentified Man #1: 911 Emergency, what are you reporting?

Mr. SAYLOR'S BROTHER-IN-LAW: We're going north, 125.

Unidentified Man #1: Um-hum.

Mr. SAYLOR'S BROTHER-IN-LAW: And our accelerator is stuck.

Unidentified Man #1: I'm sorry?

Mr. SAYLOR'S BROTHER-IN-LAW: Our accelerator is stuck. We're in trouble. We can't - there's no brakes.

SPIEGEL: People listened to this call of Mark Saylor and his family speeding to their deaths, and it changed their view of driver error.

Mark Saylor was clearly calm enough to make a phone call and explain his problem. Suddenly cars, not people, were to blame.

(Soundbite of news broadcast)

Unidentified Woman: Could a floor mat have caused this tragic Southern California crash?

(Soundbite of news broadcast)

Unidentified Man #2: Many owners now suspect there's some kind of glitch in the computer that controls the Toyota acceleration system.

SPIEGEL: So the narrative has changed. But some experts still believe that human errors are probably part of the problem.

Walter Wierwille is one. A former professor of systems engineering at Virginia Tech. back in the '80s, he was one of the first people to look into this subject. And he says that initially, experts thought pedal error was really rare. So Wierwille decided to do a test. He placed video cameras in car simulators, then used the local paper to recruit drivers. And what he found about pedal error was pretty surprising.

Professor WALTER WIERWILLE (Virginia Tech): An error might generally occur once every half-hour or one hour. And the errors, the great majority of them, are not serious errors.

SPIEGEL: People might lightly tap the wrong pedal with their foot. But he also did find some few cases where people just chose the wrong pedal. But he says in his study, these were rare.

Mr. WIERWILLE: Across the entire experiment, we had a couple of instances where this occurred. That wouldn't be sufficient to draw any conclusions.

SPIEGEL: So could people really just mistake their gas pedals for brake pedals in a way that caused accidents?

This question was answered by a human performance psychologist at UCLA named Richard Schmidt. Schmidt carefully combed through all the accident reports in the state of North Carolina for a seven-year period.

Mr. RICHARD SCHMIDT (UCLA): In the seven-year period that we studied, there was something like 3,700 pedal error accidents. The driver hit the accelerator intending to hit the brake, and crashed into the car in from of them.

SPIEGEL: But here's the question that neither Wierwille nor Schmidt ever answered: People make errors, but do they make sustained errors? Could you hurtle down a highway for minutes at a time, mistakenly pressing the wrong pedal?

No one has done experiments specifically on sustained error with car pedals. But psychologists looking at people under intense stress have found that people sometimes repeat the same error over and over again. This is particularly likely when people have misdiagnosed the problem.

Psychologist Chris Wickens says a good example of this is Three Mile Island. The nuclear engineers thought a cooling valve was closed when it was actually open.

Mr. CHRIS WICKENS (Psychologist): And as a result, they ignored other sources of evidence that said, no, the pressure's not too high, it's actually getting too low. And so they continued with the wrong form of behavior until things reached a crisis situation.

SPIEGEL: Could someone keep pressing the gas pedal as the car speeds up? In the March 9th New York accident, the driver told the police the car sped up on its own despite her braking.

Alix Spiegel, NPR News, Washington.

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