The JRC's report argued that diesel cars should be tested on the road, rather in the lab, to reduce the risk of manipulation. "Sensors and electronic components in modern light-duty vehicles are capable of 'detecting' the start of an emissions test in the laboratory,'' it said. The devices could also "activate, modulate, delay, or deactivate emissions control systems",' the report warned. Moving to on-road testing should ensure "that the use of defeat strategies is decreased as far as possible''.
On-road emissions tests conducted by the JRC "show that the real-world nitrogen oxides (NOx) emissions of . . . light-duty diesel vehicles substantially exceed the regulatory emissions standards,'' the study added. "The existing on-road tests unequivocally point to weaknesses in the current type-approval procedure.''
Since the EU banned defeat devices in 2007, the European Commission has attempted to introduce legislation to test diesel cars in a more realistic "real-world" environment. It argues that these new on-the-road tests will be able to counter the effect of illegal software.
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However, green groups and members of the European Parliament have protested that these reforms have been delayed for eight years by the powerful diesel lobby.
Greenpeace complained that, according to publicly available data, diesel manufacturers had spent as much as €18.5m lobbying Brussels in 2014, employing 184 lobbyists.
"As evidence emerges that the German government and the European Commission knew about the test-cheating software, people will be wondering why it took the Americans to expose it. The extent of the carmakers' lobbying power could provide some clues to the answer," said John Sauven, executive director of Greenpeace UK.
Two EU officials observed that there was nothing new in mid-level technical officials flagging their worries about a seemingly doctored test environment. However, attempts to act on those fears never gained much traction in a highly politicised commission environment, one said.
Authorities across Europe have been passing the buck over who is responsible. The European Commission argues that it has no power to force the national authorities to look for default devices. But Germany has responded to a question about the cheating in tests by citing the view of the commission that there was no agreed method for preventing the use of illegal software.
Christofer Fjellner, a Swedish parliamentarian, said it was unacceptable for Brussels to pass the blame entirely to member states.
"The commission is responsible for seeing we have a control framework that works. We know there are companies that don't give a damn about the rules," he said.
A spokeswoman for the European Commission said: "When it comes to policing of companies' compliance with EU law and investigative powers that is for the national authorities in this area.''
"We are inviting all member states to carry out investigations,'' she said, adding that the commission's role was to act as a "a platform to facilitate the exchange of information between member state authorities".
Officials from national transport ministries and the commission will discuss the issue on October 6, when there will be a discussion on expanding the scope of the investigation beyond VW.