Sudden unintended acceleration
Sudden Unintended Acceleration (SUA) is the unintended, unexpected, uncontrolled acceleration of a vehicle from a stationary position, low initial speed or at cruising speed, often accompanied by an apparent loss of braking effectiveness. It is unclear whether problems are caused by driver error (e.g., pedal misapplication), mechanical or electrical problems with automobiles, or some combination of these factors.

Definition and background

In the 1980s, the U.S. National Highway Traffic Safety Administration
National Highway Traffic Safety Administration
The National Highway Traffic Safety Administration is an agency of the Executive Branch of the U.S. government, part of the Department of Transportation...

 (NHTSA) reported a narrow definition of sudden acceleration only from near standstill in their 1989 Sudden Acceleration Report:

"Sudden acceleration incidents" (SAI) are defined for the purpose of this report as unintended, unexpected, high-power accelerations from a stationary position or a very low initial speed accompanied by an apparent loss of braking effectiveness. In a typical scenario, the incident begins at the moment of shifting to "Drive" or "Reverse" from "Park".

The report is taken from a study, begun in 1986, in which the NHTSA examined ten vehicles suffering from an "above average" number of incident reports and concluded that those incidents must have resulted from driver error. In the lab tests, throttles were positioned to wide open prior to brake application in an attempt to replicate the circumstances of the incidents under study. However, it is important to note that the newest vehicle involved in the study was a 1986 model and that no test vehicles were equipped with manual transmissions or the electronic control (drive by wire
Drive by wire
Drive-by-wire, DbW, by-wire, or x-by-wire technology in the automotive industry replaces the traditional mechanical control systems with electronic control systems using electromechanical actuators and human-machine interfaces such as pedal and steering feel emulators...

) systems common in 2010.

These tests were meant to simulate reports of the time suggesting that the vehicles were at a standstill and accelerated uncontrollably when shifted from park. With modern drive by wire fuel controls, problems are believed to occur exclusively while the vehicle is under way.

In the 1950s, General Motors automobiles with automatic transmission
Automatic transmission
An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...

s placed the R for reverse at the furthest clockwise position in the rotation of the column-mounted shift lever. L for low position was just adjacent as one would move the lever one notch counterclockwise. Because it was very easy to select L, a forward position when desiring R, to reverse, there were many unintended lurches forward while the driver was watching toward the rear, expecting to reverse the automobile. By the 1960s, gear selection arrangements became standardized in the familiar PRNDL, with reverse well away from the forward positions and between the Park and Neutral selections. The elimination of 'push-button' drive control on all Chrysler products began after 1965 to eliminate the ease of selecting an unintended direction.

Possible factors

Sudden unintended acceleration incidents often involve the simultaneous failure of a vehicle's acceleration and brake systems. Acceleration system factors may include:
  • Pedal misapplication
  • Unresponsive (entrapped) pedals
  • Electronic throttle control
    Electronic throttle control
    Electronic throttle control is an automobile technology which severs the mechanical link between the accelerator pedal and the throttle. Most automobiles already use a throttle position sensor to provide input to traction control, antilock brakes, fuel injection, and other systems, but use a...

     or cruise control failure (see drive by wire
    Drive by wire
    Drive-by-wire, DbW, by-wire, or x-by-wire technology in the automotive industry replaces the traditional mechanical control systems with electronic control systems using electromechanical actuators and human-machine interfaces such as pedal and steering feel emulators...

  • Stuck throttle (unrelated to pedal position)

Unintended acceleration resulting from pedal misapplication is a driver error
Human reliability
Human reliability is related to the field of human factors engineering and ergonomics, and refers to the reliability of humans in fields such as manufacturing, transportation, the military, or medicine...

 wherein the driver presses the accelerator when braking is intended. Some shorter drivers' feet may not be long enough to touch the floor and pedals, making them more likely to press the wrong pedal due to a lack of proper spatial or tactile
Haptic perception
Haptic perception is the process of recognizing objects through touch. It involves a combination of somatosensory perception of patterns on the skin surface and proprioception of hand position and conformation....

 reference. Pedal misapplication may be related to pedal design and placement, as in cases where the brake and accelerator are too close to one another, or the accelerator pedal too large.

An unresponsive accelerator pedal may result from incursion
Incursion is a science fiction role playing game created by Richard Tucholka and published by Tri Tac Games in 1992.-Overview:The player characters are humans abducted by alien slave traders...

: i.e., blockage by a foreign object, or any other mechanical interference with the pedal's operation — and may involve the accelerator or brake pedal
Automobile pedal
An automobile may have two to four foot pedals. The arrangement is the same for both right- and left-hand traffic. From left to right:* normally operated by the left foot:**clutch pedal, not in the case of automatic transmission...

. Throttle butterfly valves may become sluggish in operation or may stick in the closed position. When the driver pushes harder on the right foot, the valve may "pop" open to a point greater than that wanted by the driver, thus creating too much power and a lurch forward. Special solvent sprays are offered by all manufacturers and aftermarket jobbers to solve this very common problem.

Other problems may be implicated in the case of older vehicles equipped with carburetor
A carburetor , carburettor, or carburetter is a device that blends air and fuel for an internal combustion engine. It is sometimes shortened to carb in North America and the United Kingdom....

s. Weak, disconnected, or mis-connected throttle return springs, worn shot-pump barrels, chafed cable housings, and cables which jump their tracks in the throttle-body crank can all cause similar acceleration problems.

For drive-by-wire automobiles, a brake-accelerator interlock switch, or "smart throttle" would eliminate or at least curtail any instance of unintended acceleration not a result of pedal misapplication by causing the brake to override the throttle. An unintended acceleration event would require the failure of such a mechanism if it were present. Such a solution would not be applicable to older vehicles lacking a drive-by-wire throttle.

Analyses conducted in the mid to late 1990s on Jeep Cherokee and Grand Cherokee vehicles concluded that hundreds of reported sudden accelerations in these vehicles were likely caused by an undesired current leakage pathway that resulted in actuation of the cruise control servo. When this occurred, typically at shift engage (moving the shift lever from park to reverse), the engine throttle would move to the wide open position. While the brakes were operational, operator response was often not quick enough to prevent an accident. Most of these events occurred in close confines in which rapid operator response would be necessary to prevent striking a person, fixed object or another vehicle. Many of these events occurred at car washes, and the Jeep Grand Cherokee continues to experience sudden acceleration at car washes across the country. A statistical analysis of SAIs in 1991 through 1995 Jeeps revealed that the root cause of these incidents could not be human error, as had been historically posited by NHTSA and auto manufacturers.

Reported incidents

Reported incidents of sudden acceleration, include:
  • 1988: 1986 Honda Accord
    Honda Accord
    The Honda Accord is a series of compact, mid-size and full-size automobiles manufactured by Honda since 1976, and sold in a majority of automotive markets throughout the world....

    s were documented to have had sudden acceleration incidents due to the Vehicle Speed Control component, as reported to the NHTSA.
  • 1997: Sudden acceleration in Jeep Cherokee
    Jeep Cherokee (XJ)
    The Jeep Cherokee is a unibody compact SUV. It shared the name of the original full-size SJ model, but without a body-on-frame chassis, it set the stage for the modern SUV. Its innovative appearance and sales popularity spawned important imitators as other automakers began to notice that this...

    s and Jeep Grand Cherokee
    Jeep Grand Cherokee
    The Jeep Grand Cherokee is a Mid-size SUV produced by the Jeep division of Chrysler. While some other SUVs were manufactured with body on frame construction, the Jeep Grand Cherokee has always used a unibody chassis.- Development :...

    s was reported by Diane Sawyer
    Diane Sawyer
    Lila Diane Sawyer is the current anchor of ABC News' flagship program, ABC World News. Previously, Sawyer had been co-anchor of ABC Newss morning news program, Good Morning America ....

     in a March 1997 ABC News
    ABC News
    ABC News is the news gathering and broadcasting division of American broadcast television network ABC, a subsidiary of The Walt Disney Company...

     Primetime segment.
  • 2000: Several Ford Explorer
    Ford Explorer
    The Ford Explorer is a sport-utility vehicle sold in North America and built by the Ford Motor Company since 1990, as a replacement for the smaller but related Ford Bronco II. It is manufactured in Chicago, Illinois...

    s were reported about in the UK by a Channel 4
    Channel 4
    Channel 4 is a British public-service television broadcaster which began working on 2 November 1982. Although largely commercially self-funded, it is ultimately publicly owned; originally a subsidiary of the Independent Broadcasting Authority , the station is now owned and operated by the Channel...

     news program where the vehicle was already moving at speed and experienced sudden acceleration.
  • 2006: The 2004 Ford Mustang Cobra was recalled by Ford for accelerator pedals that failed to return to idle after being fully pressed.
  • 2008: Incidents involving the 2005 Kia Amanti and Kia Sephia
    Kia Sephia
    The Kia Sephia is a compact car that was manufactured by the South Korean automaker Kia Motors from September 1992 to 2003. The name "Sephia" is an acronym of these words: "style", "elegant", "powerful", "hi-tech", "ideal", and "auto"....

     had been reported that were preceded by a racing or highly-revving engine.
  • 2009: Toyota Avalon displays unintended acceleration without floor mat; observed by dealer
  • 2009-2010: Several vehicles were recalled in the 2009–2010 Toyota vehicle recalls
    2009–2010 Toyota vehicle recalls
    Three separate but related recalls of automobiles by Toyota Motor Corporation occurred at the end of 2009 and start of 2010. Toyota initiated the recalls, the first two with the assistance of the U.S. National Highway Traffic Safety Administration , after reports that several vehicles experienced...

    , which resulted in suspension of production and sales of many of Toyota's most popular models, including the Toyota Corolla
    Toyota Corolla
    The Toyota Corolla is a line of subcompact and compact cars manufactured by the Japanese automaker Toyota, which has become very popular throughout the world since the nameplate was first introduced in 1966. In 1997, the Corolla became the best selling nameplate in the world, with over 35 million...

    , Toyota Camry
    Toyota Camry
    The Toyota Camry is a series of mid-size automobiles manufactured by Toyota since 1982, and sold in the majority of automotive markets throughout the world...

    , Toyota Tacoma
    Toyota Tacoma
    The Toyota Tacoma is a pickup truck produced and manufactured by the Toyota Motor Corporation since 1995. The Tacoma was a compact pickup until a model redesign in 2005 when it was reclassified to a mid-size...

     pickups, Toyota Avalon
    Toyota Avalon
    The Toyota Avalon is a full-size car produced by Toyota in the United States, and is the flagship sedan of Toyota in the United States, Canada, Puerto Rico and the Middle East. It was also produced in Australia from 2000 until July 2005 when it was replaced in November 2006 by the Toyota Aurion...

    , Toyota Matrix
    Toyota Matrix
    The Toyota Matrix, sometimes officially referred to as the Toyota Corolla Matrix, is a compact hatchback manufactured by the Toyota Motor Corporation in Canada, to be sold in the United States, Canada, and Mexico...

    , Pontiac Vibe
    Pontiac Vibe
    The Pontiac Vibe is a compact hatchback car that was produced in Fremont, California, in the United States by NUMMI , a joint venture between General Motors and Toyota, and marketed under General Motors' Pontiac brand...

    , and more.

Audi 5000

During model years 1982-1987, Audi issued a series of recalls of Audi 5000 models associated with reported incidents of sudden unintended acceleration linked to six deaths and 700 accidents. At the time, National Highway Traffic Safety Administration ( NHTSA)
National Highway Traffic Safety Administration
The National Highway Traffic Safety Administration is an agency of the Executive Branch of the U.S. government, part of the Department of Transportation...

 was investigating 50 car models from 20 manufacturers for sudden surges of power.

60 Minutes
60 Minutes
60 Minutes is an American television news magazine, which has run on CBS since 1968. The program was created by producer Don Hewitt who set it apart by using a unique style of reporter-centered investigation....

aired a report titled "Out of Control" on November 23, 1986, featuring interviews with six people who had sued Audi after reporting unintended acceleration, including footage of an Audi 5000 ostensibly displaying a surge of acceleration while the brake pedal was depressed. Subsequent investigation revealed that 60 Minutes had not disclosed they had engineered the vehicle's behavior — fitting a canister of compressed air on the passenger-side floor, linked via a hose to a hole drilled into the transmission — the arrangement executed by one of the experts who had testified on behalf of a plaintiff in a then pending lawsuit against Audi's parent company.

Audi contended, prior to findings by outside investigators, that the problems were caused by driver error, specifically pedal misapplication. Subsequently, the National Highway Traffic Safety Administration (NHTSA) concluded that the majority of unintended acceleration cases, including all the ones that prompted the 60 Minutes report, were caused by driver error such as confusion of pedals. CBS did not acknowledge the test results of involved government agencies, but did acknowledge the similar results of another study.

With the series of recall campaigns, Audi made several modifications; the first adjusted the distance between the brake and accelerator pedal on automatic-transmission models. Later repairs, of 250,000 cars dating back to 1978, added a device requiring the driver to press the brake pedal before shifting out of park. As a byproduct of sudden unintended acceleration, vehicles now include gear stick
Gear stick
A gear stick is the lever used to change gear in a vehicle, such as an automobile, with manual transmission or several common forms of automatic transmission.The device is used to change gear; in a manual transmission vehicle this will normally be done whilst depressing...

 patterns and brake interlock mechanisms to prevent inadvertent gear selection.

Audi’s U.S. sales, which had reached 74,061 in 1985, dropped to 12,283 in 1991 and remained level for three years. — with resale values falling dramatically. Audi subsequently offered increased warranty protection and renamed the affected models — with the 5000 becoming the 100 and 200 in 1989. The company only reached the same level of U.S. sales again by model year 2000.

As of early 2010, a class-action lawsuit filed in 1987 by about 7,500 Audi Audi 5000-model owners remains unsettled and is currently contested in county court in Chicago after appeals at the Illinois state and U.S. federal levels. The plaintiffs in this lawsuit charge that on account of the sudden acceleration controversy, Audis had lost resale value.

See also

  • Automobile safety defect
  • Automotive accident
  • Electronic stability control
    Electronic stability control
    Electronic stability control is a computerized technology that may potentially improve the safety of a vehicle's stability by detecting and minimizing skids. When ESC detects loss of steering control, it automatically applies the brakes to help "steer" the vehicle where the driver intends to go...

    , comprehensive drive by wire safety systems
  • George Russell Weller
    George Russell Weller
    George Russell Weller was a retired salesman from Santa Monica, California, who gained notoriety as the motorist in a fatal car accident, fueling a national debate in the United States on safety risks posed by elderly drivers.On October 20, 2006, Weller was found guilty of 10 counts of vehicular...

  • Product recall
    Product recall
    A product recall is a request to return to the maker a batch or an entire production run of a product, usually due to the discovery of safety issues. The recall is an effort to limit liability for corporate negligence and to improve or avoid damage to publicity...


External links

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