Unintended acceleration

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

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".

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.

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