After thousands of complaints, investigations worldwide spanning more than 30 years and the recall of millions of vehicles, the problem of sudden unintended acceleration isn't close to being resolved.
The National Highway Traffic Safety Administration has been grappling with the issue since the late 1970s, opening more than 100 investigations involving 20 automakers and closing nearly all without taking action.
In recent weeks, Toyota Motor Corp. has struggled to put behind it reports of runaway vehicles that prompted the worldwide recall of more than 9 million vehicles.
"There appears to be a growing body of evidence that neither Toyota nor NHTSA have identified all the causes of sudden unintended acceleration in Toyota vehicles," said investigators for the House Oversight Committee, which will hold a hearing.
Over recent decades, the issue has sparked hundreds of lawsuits, numerous settlements and countless design changes aimed at reducing the incidents.
Ford is appealing an $18 million 2006 jury award in Greenville, stemming from a crash that paralyzed a 17-year-old girl and killed her aunt. The jury said the Ford Explorer's faulty cruise control system caused it to speed out of control . Ford blames driver error and reiterated this week that "despite years of NHTSA research, a few plaintiffs attorneys continue to promote the phenomenon of alleged sudden acceleration."
Automakers have issued dozens of fixes, from replacing floor mats and pedals to installing fail-safe systems such as brake interlocks and overrides.
"There's no one easy reason to explain all of these unintended acceleration cases," said Sean Kane, an automotive safety consultant at Safety Research & Strategies who will testify at the hearing. "But we know how the lessons learned from the past have often been missed."
In August 1978, NHTSA opened an investigation into whether General Motors cars were prone to sudden acceleration.
Eight years and 1,500 complaints later, after looking at 60 million GM vehicles built between 1971 and 1986, NHTSA concluded there was "strong evidence" that driver error was to blame for many of the crashes.
It closed its investigation without ordering a recall.
But the issue didn't go away.
By 1986, more than 2,000 injuries industrywide had been blamed on unintended acceleration; more than 10 percent of all complaints to NHTSA were sudden acceleration claims.
The agency called for design changes, including moving gas and brake pedals farther apart, and adding brake-shift interlocks that require a driver to engage the brake before shifting into gear, reducing the risk of unintended motion.
Automakers voluntarily agreed in 2007 to add a brake-shift interlock system - and Congress mandated it in 2008. Starting this year, the devices will be installed in all vehicles, up from about 80 percent of 2006 models.
Since 1999, NHTSA has launched numerous new investigations into runaway vehicles.
Kane says NHTSA hasn't scrutinized vehicle electronics. But last week, NHTSA said it was taking yet another look at whether electronic issues might have played a role in Toyota's sudden acceleration incidents, and it was reviewing other automakers, too.