systems were prone to defects which resulted in excessive idle speeds and brief unanticipated accelerations of up to 0.3g [which is similar in magnitude to an emergency stop in a subway car]. These accelerations could not be the sole cause of [(long-duration) sudden acceleration incidents (SAI)], but might have triggered some SAIs by startling the driver. The defective idle-stabilization system performed a type of electronic throttle control. Significantly: multiple "intermittent malfunctions of the electronic control unit were observed and recorded ... and [were also observed and] reported by Transport Canada." With a 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. A legacy of the Audi 5000 and other reported cases of sudden unintended acceleration are intricate gear stick patterns and brake interlock mechanisms to prevent inadvertent shifting into forward or reverse. It is unclear how the defects in the idle-stabilization system were addressed. 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 – and reached the same sales levels again only by model year 2000. A 2010 BusinessWeek article – outlining possible parallels between Audi's experience and 2009–2010 Toyota vehicle recalls – noted a class-action lawsuit filed in 1987 by about 7,500 Audi 5000-model owners remains unsettled and remains contested in Chicago's Cook County after appeals at the Illinois state and U.S. federal levels. Model introductions In the mid-to-late 1990s, Audi introduced new technologies including the use of aluminium construction. Produced from 1999 to 2005, the Audi A2 was a futuristic super mini, born from the Al2 concept, with many features that helped regain consumer confidence, like the aluminium space frame, which was a first in production car design. In the A2 Audi further expanded their TDI technology through the use of frugal three-cylinder engines. The A2 was extremely aerodynamic and was designed around a wind tunnel. The Audi A2 was criticised for its high price and was never really a sales success but it planted Audi as a cutting-edge manufacturer. The