Sudden Unintended Acceleration

Sudden unintended acceleration (SUA) is a flaw that occurs when a car abruptly accelerates as a driver is shifting gears or adjusting cruise control, even if the driver is applying the brakes. It often results in serious harm to both the driver of the malfunctioning vehicle and the passengers of nearby vehicles. Faulty design in the electronic acceleration system of many cars prevents the software from identifying and counteracting malfunctions that cause SUA. Because of this, a car’s computer will not show an error message when the sudden acceleration occurs, nor will it deactivate the system that sent the signal to accelerate. This can easily cause serious damages, even fatalities, to those who drive cars with electronic acceleration systems.

However, all car manufacturers whose designs have been called into question deny any relationship between their system and SUA, claiming that human error is to blame because SUA incidents are more common among elderly or inexperienced drivers, and are rarely found in cars driven by short, middle-aged men. Many of these accidents also occur within a single region of the country, a fact that also supports the manufacturers’ claims. Other factors that receive blame in these cases include sticky gas pedals and pedals that get caught by improperly installed floor mats. It is possible that drivers who recently switched cars or are not accustomed to cruise control could be more susceptible to SUA because the position of the brake and gas pedals could different and the driver could easily confuse the two, while cruise control may just be a complicated feature for inexperienced drivers to figure out.

The argument between human error and faulty computers will continue, though several cases may be solved by an event data recorder (EDR), or black box. The information stored in a black box would help determine a car’s speed, as well as the amount of throttle or braking applied by the driver at the time of the accident. However, because this feature is not used in all cars, nor is it a consistently accurate device, the EDR cannot yet be used to solve accidents involving SUA.

One of the main manufacturers under scrutiny is Toyota, though other companies such as Ford and General Motors are not immune to lawsuits. Many have claimed that their Toyota vehicle did not record an error code when the SUA occurred, but maintain that the car’s electronic acceleration system prevented the onboard computer from detecting and stopping the short circuits that could cause SUA. Toyota has stated in press releases that there are no electronic or mechanical problems related to SUA, and that the accidents were all undeniably caused by driver error, sticky gas pedals, or pedals trapped by floor mats.

The National Highway Traffic Safety Administration states:

“The NHTSA's official Administration has its own perspective view is that the vast majority of sudden acceleration incidents in which no vehicle malfunction is present are caused by drivers mistaking the gas pedal for the brake. However the NHTSA continues to investigate all potential causes for sudden acceleration, including the electronic throttle control system in Toyota vehicles…Safety regulators, human-error experts and auto makers say driver error is the primary cause of sudden accelerations, and if there are no error codes in the electronics, there is no evidence to support an electronic failure.”


Linebaugh, K. and D. Searcey. 2010. "Cause of Sudden Acceleration Proves Hard to Pinpoint". The Wall Street Journal. http://online.wsj.com/article/SB10001424052748703510204575085531383717288.html?KEYWORDS=sudden+acceleration.

O'Donnell, J. and D. Kiley. 2004. “Technology puts unintended acceleration back in spotlight”. USA Today. http://www.usatoday.com/money/autos/2004-04-13-unintended-acceleration_x.htm