Unintended sudden acceleration theories

The unintended sudden acceleration problem that plagued Toyota in 2009-2010 and Mitsubishi last year has resurfaced in the United States and here. Last week, a lawsuit filed in Washington by a nongovernment automotive safety firm accused the National Highway Traffic Safety Administration (NHTSA) of withholding documents and videos that might depict an acceleration incident caused by electronic systems in a 2003 Prius instead of by the floor mats or pedals covered by Toyota’s recalls of more than eight million vehicles worldwide three years ago.

Over here, a relatively unknown TV show about motoring is repeatedly showing a video clip of a Mitsubishi Montero Sport (MS) inside a drugstore after it allegedly over-accelerated and crashed out of control into the drugstore, hitting display shelves and scattering merchandise on the floor. No one was injured, according to the SUV’s owner. The TV show would revive alarm about the MS’ sudden acceleration problem that was first triggered in February 2011 by Internet blogs claiming that their MS units revved and sped up uncontrollably upon shifting from Park to Drive and ended up crashing into structures and other cars even with the driver’s foot firmly on the brake pedal. The MS, by the way, is the second-best-selling motor vehicle in the Philippines after the Toyota Vios, having surpassed midsize SUV segment leader Toyota Fortuner in sales.

In an official statement, Mitsubishi Motors Philippines Corp. (MMPC) said that upon receiving the sudden acceleration complaints, Mitsubishi Motors Japan sent engineers in February 2011 to investigate. The results showed that all the MS’ components—the fuel injection system, pedal, Engine Control Unit (ECU), wiring harness, etc.—and software are operating normally within specs. Mitsubishi noted that the electronic throttle system of the MS had undergone extensive testing not only during its development, but also during mass production to ensure that it will function the way it was designed to. MMPC invited MS owners bothered by the blogs to bring their unit to any MMPC service center nationwide for a free checkup. MMPC also encouraged every owner/driver to read the owner’s manual for important reminders on the proper driving procedure, most especially for automatic transmission vehicles.

Audi

Unintended sudden acceleration is nothing new. The issue nearly destroyed Audi some 20 years ago because of fabricated TV coverage of the unintended acceleration of an Audi 5000 (the predecessor of the A6) by the CBS News show, “60 Minutes.” After the fraudulent manipulation of the car was exposed and Audi was vindicated by the NHTSA and after Audi told the world the truth in full-page ads, it took more than a decade for Audi to return to its pre-“60 Minutes” sales levels in the US.

As for Toyota, in May 2010 the carmaker paid a record-setting $16.4-million fine to the US Department of Transportation for not notifying the NHTSA of potential defects in a timely manner. US law requires any car company aware of a safety defect to advise the NHTSA within five days. A class action suit versus Toyota in the US claimed that the company knew about the unintended acceleration issue as early as 2003.

Last year, according to a recent report in the International Herald Tribune, the NHTSA closed its investigation of Toyota without finding defects in the brand’s electronic throttle systems. Instead, the agency, which reviews 40,000 consumer complaints a year, concurred with Toyota’s explanation that faulty floor mats and sticky accelerator pedals—if not driver error—had caused Toyota vehicles to accelerate suddenly out of control.

Ill-equipped

The National Aeronautic and Space Administration reached the same conclusion in a separate study. But while a branch of the National Academy of Sciences announced last week that there was no evidence of  electronic malfunction in Toyotas, it also concluded that US regulators are ill-equipped to detect problems in the complex computer systems of modern cars.

That conclusion is shared by Dr. Antony Anderson, a fellow of the Institution of Engineering and Technology and of the Institution of Diagnostic Engineers. An electrical engineering consultant and electrical expert witness (UK and North America), Anderson says there are only two possible ways in which the throttle can open and cause sudden acceleration from near standstill: 1) driver malfunction or “pedal error” hypothesis: If the driver for some reason depresses the accelerator pedal to the floor or 2) electronic system malfunction hypothesis: If the cruise control servo or the electronic throttle servo, in the case of an electronic throttle system, moves the throttle to the open position uncommanded.

These two possibilities—driver malfunction and electronic malfunction—are mutually exclusive, Anderson points out. Proponents of the “driver pedal error” hypothesis contend that where no physical evidence of a failed electronic component is found after the event, there could not have be an electronic malfunction and therefore the only plausible explanation is that it was the driver that malfunctioned.

This is an example of the fallacy “Absence of proof is proof of absence,” Anderson argues. In fact, he says, “Absence of proof is not proof of absence” as intermittent electronic malfunctions do not necessarily leave permanent traces behind them after the event and may not be reproduceable on demand.

Malfunction

In product liability cases, Anderson continues, a common defense against a claim of an electronic malfunction is driver malfunction. The defense asserts that the driver pressed the accelerator pedal in the belief that he/she was applying the brake pedal, thus causing the vehicle to accelerate. The pedal error hypothesis is presented as if supported by solid evidence of the absence of an electronic component failure—when in fact there is no such evidence, Anderson says.

If, for argument’s sake, sudden acceleration were the result of “pedal error,” then clearly the vehicle did not play a part in causing it, Anderson goes on. If sudden acceleration were in no way related to the vehicle, this should immediately become apparent from a study of sudden acceleration complaint databases. In other words, the incidence rate of sudden acceleration per 100,000 vehicles should be more or less the same for all ages and makes of cars. There would be little difference in the sudden acceleration rates of vehicles of different makes, of the same make but different marques, of different model years, fitted with manual or automatic gearboxes, with or without cruise control, with or without electronic throttle control.

The sudden acceleration incidence rate appears to vary widely between vehicles of different manufacture and between vehicles of the same type but different model years. This strongly suggests that whatever the factors are that cause sudden acceleration, these are related to the vehicle rather than the driver, Anderson concludes.