So-called 'sudden acceleration' has a long and unfortunate history, almost destroying Audi sales in the mid-1980s after 60 Minutes accused the Audi 5000 of accelerating out of control at random.
Now, as previewed a few weeks ago, an NHTSA report finds no electronic cause for the phenomenon--and suggests that in the cases that involve Toyota vehicles fitted with event data recorders, or 'black boxes,' the accidents have been due to driver error.
Black boxes: No braking
Starting in 2007, various Toyota models have been fitted with black boxes that record a few seconds of the car's control inputs once an airbag has been deployed.
While this limits the number of accidents that can be analyzed, the results are still revealing. Of 58 data recorders analyzed by teams from both the NHTSA and Toyota, 35 showed that when the crash occurred, the brake pedal was not depressed at all.
Another 14 showed only partial braking, and 9 more indicated braking only just before the accident. The report said brakes were pressed and released, or both brake and accelerator were pressed together, in a handful of crashes.
Drivers may not actually know what pedal they're pressing during an emergy, explains Richard Schmidt, a psychology professor at the University of California, Los Angeles.
In an article in The New York Times, Schmidt noted that "sudden acceleration is very often caused by drivers who press the gas pedal when they intend to press the brake."
Loose all-weather floor mat jams accelerator pedal. Photo: NHTSA
Toyota's diagram showing how to properly install floor mats
Only a subset of crashes
A plaintiff-lawyers' group, on the other hand, scoffed at the notion that the report exonerated Toyota in any way. It noted two concerns with the data presented from the subset of cases that involved event data recorders.
First, the NHTSA report does not address many of the complaints that occurred in pre-2007 cars and, second, many of the crashes occurred at speeds too low to trigger the airbag, meaning no data was recorded.
While the report may help allay concerns of widespread software flaws in Toyotas, the company is still dealing with recalls stemming from two known issues that have contributed to a small number of cases not attributed to driver error.
Two known causes
Those are "sticky" accelerator pedals that may rust to the point where they don't return to idle, and fitting of unapproved or aftermarket floor mats that can wedge accelerator pedals to the floor if they shift out of position.
In the case of the sticky pedals, attributed to an unapproved materials substitution by a U.S. parts supplier, Toyota has recalled the affected vehicles and is replacing the accelerator mechanism.
As for the floor-mat problem--believed to be the cause of a horrific crash last year in which a California Highway Patrol officer and his family were killed when their Lexus crashed and burned after accelerating to high speed--Toyota is shortening accelerator pedals in the affected vehicles so they cannot be entrapped no matter what floor mats are fitted.
Almost 10 million recalled
In the last year, Toyota has recalled 9.4 million vehicles worldwide to fix these two issues, including 7.5 million in the U.S.
An NHTSA statement carefully notes that the agency has "drawn no conclusions about additional causes of unintended acceleration in Toyotas beyond the two defects already known: pedal entrapment and sticky pedals."
And the agency stressed it is continuing to investigate the accidents, as is Toyota itself. The agency and NASA are testing whether electromagnetic radiation may interfere with vehicle electronics, bombarding vehicles with EMR at a Chrysler test facility.
For more information on those causes and Toyota's responses, see our summary, Toyota And Lexus Recall: Everything You Need To Know, which provides full details on the two largest recalls in North America to address accelerator pedal issues.