A diesel whodunit: How software let VW cheat on emissions

Volkswagen AG CEO Martin Winterkorn announced today he is stepping down as the result of his company's cheating on emission tests, bypassing environmental standards and landing the company in regulatory hot water.
According to the U.S. Environmental Protection Agency, Volkswagen was able to cheat emissions tests for half a million of its U.S.-sold cars. The software that enabled cars to thwart emissions tests is in as many as 11 million other vehicles, Volkswagen admitted Tuesday.
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