Sudden unintended acceleration

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Sudden unintended acceleration (SUA) is the unintended, unexpected, uncontrolled acceleration of a vehicle, often accompanied by an apparent loss of braking effectiveness.[1] Such problems may be caused by driver error (e.g., pedal misapplication), mechanical or electrical problems, or some combination of these factors.[2]

Definition and background[edit]

In the 1980s, the U.S. National Highway Traffic Safety Administration (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".[1]

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 the electronic control (drive by wire) systems common in 2010. All vehicles were equipped with automatic transmissions, that is, no vehicles had manual transmissions with left foot clutch pedal disengagement of engine power.

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 transmissions 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.

The most prominent incidents of sudden unintended acceleration recently took place from 2000-2010 in Toyota and Lexus vehicles, resulting in as many as 89 deaths and 52 injuries.[3] The NHTSA first opened an auto defect investigation into Toyota vehicles in 2004, but the Office of Defects Investigation (ODI) within the NHTSA closed the investigation citing inconclusive evidence. Toyota also claimed that no defects existed and that the electronic control systems within the vehicles were unable to fail in a way that would result in an acceleration surge. More investigations were made but were unsuccessful in finding any defect until April 2008, when it was discovered that the driver side trim on a 2004 Toyota Sienna could come loose and prevent the accelerator pedal from returning to its fully closed position.[4] It was later discovered that both the electronic control systems and the floor mats of the affected Toyota vehicles could cause them to accelerate suddenly, and that Toyota had known about these problems but had misled consumers and continued to manufacture defective cars. In March 2014, the Department of Justice issued 1.2 billion dollars in financial penalties against Toyota in a deferred prosecution agreement.[5]

Possible factors[edit]

Sudden unintended acceleration incidents are often posited to involve the simultaneous failure of a vehicle's acceleration and brake systems. Acceleration system factors may include:

Unintended acceleration resulting from pedal misapplication is a driver error 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 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: 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. 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 carburetors. 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.[14] 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.[15]

Physical analysis conducted on Toyota’s electronic engine control system including accelerator pedal position sensors (APPSs) in 2011 showed the presence of a significant number of tin whiskers. Tin whiskers are elongated or needle-like structures of pure tin that grow from pure tin and tin alloy surfaces. Toyota's APPS were found to use tin finishes. These tin finishes can produce conductive tin whiskers capable of creating unintended electrical failures such as short circuits. The use of tin finish in Toyota's APPS is therefore a cause for concern.[13] Similarly in 2013, materials used in an automotive engine control unit (ECU) from a 2008 Toyota Tundra truck were analyzed. It was found that pure tin with a nickel underlayer was used as the connector finish in the unit, and analysis revealed tin whiskers on the connector surface. Further testing under a standard temperature-humidity cycling showed tin whisker growth, raising additional reliability and safety concerns. These studies show that poor design choices, such as the use of tin finishes, result in unintended failures.[12]

Reported incidents[edit]

Reported incidents of sudden acceleration, include:

  • 1987: The 1982-1987 Audi 5000s sales in the United States fell after recalls linked to sudden unintended acceleration. There were 700 accidents and 6 deaths.
  • 1988: 1986 Honda Accords were documented to have had sudden acceleration incidents due to the Vehicle Speed Control component, as reported to the NHTSA.[16]
  • 1997: Sudden acceleration in Jeep Cherokees and Jeep Grand Cherokees was reported by Diane Sawyer in a March 1997 ABC News Primetime segment.[17][18]
  • 2000: Several Ford Explorers were reported about in the UK by a Channel 4 news program where the vehicle was already moving at speed and experienced sudden acceleration.[19]
  • 2004: The National Highway Traffic Safety Administration (NHTSA) sent Toyota a chart showing that Toyota Camrys with electronic throttle controls had over 400% more "vehicle speed" complaints than Camrys with manual controls.[citation needed] Toyota culled out[clarification needed] 37,900 customer contact reports from the company's database that Toyota identified (via the company's complaint coding system) as potentially related to sudden unintended acceleration.[citation needed]
  • 2005: Incident observed in a Toyota Camry. The cause was initially suggested to be a tin whisker,[20] however this was later proven not to be the case.[21]
  • 2005: Ida Starr St John involved in sudden and unintended acceleration accident with her Toyota Camry. The Camry immediately accelerated without her pressing the accelerator pedal and pressing the brake pedal did nothing to stop the vehicle.
  • 2006: The 2004 model year Ford Mustang Cobra was recalled by Ford for accelerator pedals that failed to return to idle after being fully pressed.[22]
  • 2008: Incidents involving the 2005 Kia Amanti and Kia Sephia had been reported that were preceded by a racing or highly revving engine.[23][24]
  • 2009: Toyota Avalon displays unintended acceleration without floor mat; observed by dealer.[25]
  • 2009: Chase Weir's experience with sudden acceleration in his Ford Explorer while driving on a freeway was reported by a number of news organisations, along with the released 000 emergency recordings of the incident.[26]
  • 2009-2010: Several vehicles were recalled in the 2009–2010 Toyota vehicle recalls, which resulted in suspension of production and sales of many of Toyota's most popular models, including the Toyota Corolla, Toyota Camry, Toyota Tacoma pickups, Toyota Avalon, Toyota Matrix, Pontiac Vibe, and more.[27][28]

Audi 5000[edit]

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.[29] At the time, National Highway Traffic Safety Administration (NHTSA) was investigating 50 car models from 20 manufacturers for sudden surges of power.[30]

60 Minutes aired a report titled "Out of Control" on November 23, 1986,[31] 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.[32][33] 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[31][32] — 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.[34]

Audi contended, prior to findings by outside investigators that the problems were caused by driver error, specifically pedal misapplication.[30] 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.[35] CBS did not acknowledge the test results of involved government agencies, but did acknowledge the similar results of another study.[32]

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.[29] As a byproduct of sudden unintended acceleration, vehicles now include gear stick 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.[29] — with resale values falling dramatically.[36] Audi subsequently offered increased warranty protection [36] and renamed the affected models — with the 5000 becoming the 100 and 200 in 1989.[30] The company only reached the same level of U.S. sales again by model year 2000.[29]

As of early 2010, a class-action lawsuit filed in 1987 by about 7,500 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.[29] The plaintiffs in this lawsuit charge that on account of the sudden acceleration controversy, Audis had lost resale value.[32]

Sudden Acceleration in Toyota Vehicles[edit]

From 2002 to 2009 there were many defect petitions made to the NHTSA regarding unintended acceleration in Toyota and Lexus vehicles, but many of them were determined to be caused by pedal misapplication, and the NHTSA noted that there was no statistical significance showing that Toyota vehicles had more SUA incidents than other manufacturers. Other investigations were closed because the NHTSA found no evidence that a defect existed. The first major cause of unintended acceleration was found in March 2007, when an engineering analysis showed that unsecured all-weather mats had led to pedal entrapment and drivers accelerating up to 90 mph with decreased braking power. Early on, Toyota suggested that driver error was to blame, saying that some people may have hit the gas when they meant to hit the brake. Even after issuing recalls to address problematic floor mats that in some cases pinned down accelerators, the company hid a flawed gas pedal design that it knew did the same thing[37] This led to Toyota sending a letter to the owners of the affected car, a 2007 Lexus ES350, asking that they bring their cars in to switch out the all-weather mats.[38] After this recall, Toyota decided to revise the internal design of their cars to ensure that there was “a minimum clearance of 10 millimeters between a fully depressed gas pedal and the floor,” but decided to only implement the new designs upon the next “full model redesign,” which wouldn’t take place until 2010. In an attempt to hide these defects from investigators, Toyota switched to verbal communication on the defect rather than traceable forms of communication [39] As a result, many new cars were knowingly produced with the same floor mat issues that had been identified as being having the potential to cause SUA problems in association with the defective pedal design.[40]

One of those vehicles, a 2009 ES350, was given as a loaner car to CHP officer Mark Saylor on August 28, 2009. Saylor and his wife, daughter, and brother-in-law were driving on highway 125 in San Diego, California, when their car accelerated out of control and crashed into an embankment, killing everyone in the car. This crash gained nationwide news coverage due to a recorded 911 call from Chris Lastrella, Saylor’s brother-in-law. In the moments before the crash, Lastrella could be heard telling the operator that the accelerator was stuck and that the brakes wouldn’t work.[41] That exact car had experienced the same problem when Frank Bernard had driven it as a loaner car a few days earlier. Bernard told investigators that he was accelerating to get past a merging truck when the accelerator pedal jammed into the floor mat and remained there when he took his foot off the pedal. Bernard was able to slow the car down to 50-60 mph with the brakes, but was only able to bring the car to a complete stop after putting the car in neutral.[42] After this accident, Toyota conducted 7 recalls related to unintended acceleration from September 2009 to March 2010. These recalls totaled approximately 10 million vehicles and mostly switched out all-weather mats and carpet covers that had the potential to cause pedal entrapment. At this point there was little evidence that there was ever any defect in the Electronic Throttle Control System (ETCS) that was installed in Toyota cars after 2002, despite requests to the NHTSA to investigate it, and Toyota announced that the root cause of sudden acceleration had been addressed.[43]

In April 2013, Betsy Benjaminson, a freelance translator working for Toyota to translate internal documents, released a personal statement about Toyota covering up facts about the sudden unintended acceleration problem. Benjaminson stated she “read many descriptions by executives and managers of how they had hoodwinked regulators, courts, and even congress, by withholding, omitting, or misstating facts.” [44] Benjaminson also compared Toyota’s press releases and mentioned that they were obviously meant to “maintain public belief in the safety of Toyota’s cars—despite providing no evidence to support those reassurances.” This public statement was released when Benjaminson decided to name herself as a whistleblower after she had been providing evidence to Iowa Senator Charles Grassley.

This leak of internal documents fueled a criminal investigation by the FBI and the Justice Department that had been ongoing since 2010,[45] and on March 19, 2014, the DOJ issued a deferred prosecution agreement with a $1.2 billion criminal penalty for issuing misleading and deceptive statements to its consumers and federal regulators, as well as hiding another cause of unintended acceleration, the sticky pedal, from the NHTSA.[40] This fine was separate from the $1.2 billion settlement of a class action suit paid to the drivers of Toyota cars who claimed that their cars had lost value as a result of the SUA problems gaining publicity in 2012 and is the largest criminal fine against an automaker in US history.[46] Toyota was also forced to pay a total of $66.2 million in fines to the Department of Transportation for failing to handle recalls properly and $25.5 million to Toyota shareholders whose stock lost value due to recalls. Nearly 400 wrongful-death and personal injury cases were also privately settled by Toyota as a result of unintended acceleration.[46]

See also[edit]


  1. ^ a b NHTSA 1989: An Examination of Sudden Acceleration
  2. ^ "Cause of Sudden Acceleration Proves Hard to Pinpoint". The Wall Street Journal, 25 February 2010, Kate Linebaugh and Dionne Searcey. February 25, 2010. 
  3. ^
  4. ^
  5. ^
  6. ^ Highway Accident Report - Rear-End Collision and Subsequent Vehicle Intrusion Into Pedestrian Space at Certified Farmers' Market [1]
  7. ^ NHTSA January 1989 "An Examination of Sudden Acceleration" pg. 32
  8. ^ "Home | National Highway Traffic Safety Administration (NHTSA)". Retrieved 2011-11-13. 
  9. ^ Larissa Ham & Robyn Grace (2009-12-15). "Cruise control terror for freeway driver". Sydney Morning Herald. 
  10. ^ "Fact Check: Toyota not alone in acceleration problems -". CNN. February 6, 2010. Retrieved May 24, 2010. 
  11. ^ "Home | National Highway Traffic Safety Administration (NHTSA)". Retrieved 2011-11-13. 
  12. ^ a b George, Elviz; Pecht, Michael (January 2014). "Tin whisker analysis of an automotive engine control unit". Microelectronics Reliability 54 (1): 214–219. ISSN 0026-2714. 
  13. ^ a b Sood, Bhanu; Osterman, Michael; Pecht, Michael (2011). "Tin whisker analysis of Toyota's electronic throttle controls". Circuit World 37 (3): 4–9. doi:10.1108/03056121111155611. ISSN 0305-6120. 
  14. ^ "Consumer Reports - Five Key Fixes". 2010-02-05. Retrieved 2011-11-13. 
  15. ^ "Jeep NHTSA Defect Petition" (PDF). Retrieved 2011-11-13. 
  16. ^ "NHTSA Action Number: DP88008". Retrieved 2011-11-13. 
  17. ^ "Jeep Grand Cherokee SUA Incidents". Retrieved 2011-11-13. 
  18. ^ "Jeep Cherokee SUA at". Retrieved 2011-11-13. 
  19. ^ Antony Anderson. "Automobile Cruise Control Faults and Sudden Acceleration". Retrieved 2011-11-13. 
  20. ^ "An Examination of the National Highway Traffic Safety Administration and the National Aeronautics and Space Administration Engineering Safety Center Assessment and Technical Evaluation of Toyota Electronic Throttle Control (ETC) Systems and Unintended Acceleration" (PDF). Retrieved 2012-11-20. 
  21. ^
  22. ^ "2004 Ford Mustang Recalls". Retrieved 2012-06-16. 
  23. ^ cindyjo (2008-02-10). "Kia Motors Informative: Sudden acceleration - Amanti". Retrieved 2011-11-13. 
  24. ^ "Kia Sudden Acceleration". Consumer Affairs. Retrieved 2011-11-13. 
  25. ^ Kleis, Mark (2010-01-15). "Toyota Avalon displays unintended acceleration without floor mat". Left Lane News. Retrieved 2012-06-16. 
  26. ^ Cooper, Mex; Hunter, Thomas; Gregory, Peter; Millar, Paul (2009-12-16). "Cruise control terror: dramatic Triple-0 tape released". Drive. Retrieved 2012-06-28. 
  27. ^ "Toyota USA Newsroom | Safety/Recall". 2011-11-09. Retrieved 2011-11-13. 
  28. ^ [BusinessWeek March 1, 2010, pp. 14-16 "Did Toyota's Traffic Cops Sway the Regulators?"
  29. ^ a b c d e "Audi 1980s Scare May Mean Lost Generation for Toyota". Business Week, February 4, 2010, Andreas Cremer and Tom Lavell. 
  30. ^ a b c "A Hard Sell for Audi". The New York Times, John Holusha, July 24, 1988. July 24, 1988. Retrieved May 24, 2010. 
  31. ^ a b "The Audi 5000 Intended Unintended Acceleration Debacle". The Truth About Cars, Paul Niedermeyer, February 7, 2010. 
  32. ^ a b c d Huber, Peter (1989-12-18). "Manufacturing the Audi Scare". The Wall Street Journal. Retrieved 2012-06-16. 
  33. ^ Gossett, Sherrie (2005-05-13). "The CBS "Cold Case" Files". Accuracy in Media. Retrieved 2012-06-16. 
  34. ^ "Nine Worst Business Stories(of the Last 50 Years) #4. Accelerating Audis". Business and Media Institute. 
  35. ^ Yates, Brock (1989-04-16). "Unfair at Any Speed". HighBeam Research, Inc. Retrieved 2012-06-16. 
  36. ^ a b "Audi Increases Warranty Plan". The New York Times, via Reuters, July 27, 1988. July 27, 1988. Retrieved May 24, 2010. 
  37. ^ Early on, Toyota suggested that driver error was to blame, saying that some people may have hit the gas when they meant to hit the brake. Even after issuing recalls to address problematic floor mats that in some cases pinned down accelerators, the company hid a flawed gas pedal design that it knew did the same thing, according to documents accompanying the agreement.
  38. ^
  39. ^ Early on, Toyota suggested that driver error was to blame, saying that some people may have hit the gas when they meant to hit the brake. Even after issuing recalls to address problematic floor mats that in some cases pinned down accelerators, the company hid a flawed gas pedal design that it knew did the same thing, according to documents accompanying the agreement
  40. ^ a b
  41. ^
  42. ^
  43. ^
  44. ^
  45. ^
  46. ^ a b

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