European regulators didn't act after real-world emissions results were published last year showing a dozen diesel car models were an average of seven times dirtier than the standards were supposed to allow. So tests were conducted on three models in the U.S. -- two Volkswagens and a BMW -- which eventually led to the VW's admission that it rigged 11 million cars worldwide in a way that allows them to beat emissions certification tests. VW's stunning confession -- and CEO Martin Winterkorn's subsequent apology -- was the result of testing that was two years in the making, says John German, senior fellow for the International Council on Clean Transportation. The European arm of the ICCT conducted road tests in Europe and published the results late last year. When the emissions results on 12 models in Europe didn't set off alarm bells, testing was brought to the U.S. on a smaller scale because "the U.S. standards are more restrictive" and a sense that U.S. regulators are more dogged, German says. The diesel VW Jetta and Passat showed much higher levels of emissions when driven than they had on the test stand. The third car, a BMW X5, by contrast, maintained its low emissions on the road. After repeatedly denying it had a problem, VW finally told regulators that it had written software into the cars that gave them better emissions results when they were being tested than when they were being driven on the road. The U.S. Environmental Protection Agency, in calling out VW's deception, called the software a "defeat device." German says U.S. regulators didn't balk at bearing down on VW to demand answers. "That's the advantage of having strong legal authority," he says. As he watches the case unfold, German says he's struck by the mystery of why Volkswagen didn't just delete the software from the program that would have made all the cars pass real-world driving tests for emissions. "Volkswagen had the chance to get out this with a field fix," German says, a scenario in which it wouldn't have had to admit wrongdoing -- "just take the defeat device programming out of the software -- and they didn't do it." Just why is yet to be disclosed.
﻿The 'Real-world exhaust emissions from modern diesel cars' report, published by the ICCT last year, showed that a dozen diesel car models were seven times over official EU limits, which included Volkswagen ( VLKAF.PK - news - people ) and Audi ( AHOY.UL - news - people ). As a result,﻿ 11 million VW diesel cars are affected by the emissions scandal, and calls for deeper investigations﻿ into diesel car emissions﻿﻿ may reveal other car companies that have broken the ﻿rules.