NASA Can't Find Unintended Acceleration Causes in Toyota's Electronic Throttle Control System


The U.S. Department of Transportation (DoT) yesterday released the final results from NASA's Engineering and Safety Center's ten-month study into potential electronic causes of unintended acceleration (UA) in Toyota vehicles. As the DoT's press release states:

"The National Highway Traffic Safety Administration (NHTSA) launched the study last spring at the request of Congress, and enlisted NASA engineers with expertise in areas such as computer controlled electronic systems, electromagnetic interference and software integrity to conduct new research into whether electronic systems or electromagnetic interference played a role in incidents of unintended acceleration."

The DoT press release goes on to state that:

"NASA engineers found no electronic flaws in Toyota vehicles capable of producing the large throttle openings required to create dangerous high-speed unintended acceleration incidents. The two mechanical safety defects identified by NHTSA more than a year ago - "sticking" accelerator pedals and a design flaw that enabled accelerator pedals to become trapped by floor mats - remain the only known causes for these kinds of unsafe unintended acceleration incidents. Toyota has recalled nearly 8 million vehicles in the United States for these two defects."

U.S. Transportation Secretary Ray LaHood who last year famously said owners of recalled Toyota vehicles should stop driving them (before taking that statement back) now is quoted in the press release as saying that:

"We enlisted the best and brightest engineers to study Toyota’s electronics systems, and the verdict is in. There is no electronic-based cause for unintended high-speed acceleration in Toyotas."

In this Washington Post story, Secretary LaHood is even more emphatic and according to the Post, defiant:

""The jury is back, the verdict is in... There is no electronic-based cause for unintended high-speed acceleration in Toyotas. Period.' "

NASA's Engineering and Safety Center (NESC) extensively investigated Toyota's Electronic Throttle Control System Intelligent (ETCS-i - see description in PDF here) to determine if there were design and implementation vulnerabilities that could cause sudden unintended acceleration. The executive summary of the NESC team's study findings in PDF can be found here; its full report in PDF is here.

The NESC team reported that it could not find any solid evidence of sudden unintended acceleration based in its review of the NHTSA Vehicle Owners' Questionnaire (VOQ) dataset. It found that reported unintended accelerations:

"... are rare events. Typically, the reporting of UAs is about 1/100,000 vehicles / year or 1 in 1.4 billion miles. Of 426,911 total VOQ reports NHTSA received from calendar years 2000 to 2010 for all vehicle  makes and models, there were 9,698 identified as UA events based on expert review and analysis. Of these, 3,054 were for TMC [Toyota Motor Corporation] vehicles."

In examining the dataset, the NESC team did not find marked increases in UA  Vehicle Owners' Questionnaire complaints "coincident" with ETCS-i introduction in Toyota vehicles; it did find, however, increases "coincident with publicity" about UAs.

In addition, the NESC team could not find potential UA events (i.e., events that force the ETCS-i to allow wide throttle openings greater than 25 degrees) caused by abnormalities or flaws in the 280,000 lines of code in the ETCS-i, by electro-magnetic interference, by electronic failure(s), or by electrical faults.

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