These were the findings when this study was run under test conditions at Stanford University.
However, carmakers can use a whole range of techniques to ensure that their cars perform far better under test conditions than when driven by ordinary drivers.
They are now down 40% since the US Environmental Protection Agency accused the carmaker of installing a "defeat device", which reduced nitrogen oxide (NOx) emissions under test conditions.
Simulation, in industry, science, and education, a research or teaching technique that reproduces actual events and processes under test conditions.
None of the 56 vehicles tested in Germany and 37 in the UK was found to have a defeat device aimed at artificially lowering its emissions under test conditions, such as those used by VW.
The MOT test is also conducted without moving the car, so it is possible that the cars could have been similarly programmed to emit less NOx under test conditions.
Independent tests in the US have found that the energy consumption of Samsung and LG TV sets nosedives under test conditions but can soar by up to 45% in real-world use, raising questions of manipulation by software devices.
Winterkorn said on Wednesday he took full responsibility for the scandal, in which the company admitted that 11m cars were installed with a defeat device that reduced emissions under test conditions only, but he denied personal wrongdoing.
In 2000, diesel cars on the road pumped out double the NOx they did under test conditions, according to the ICCT, the group who rumbled VW's cheating in the US.
And — although this sounds crazy in an aerospace startup — especially under test conditions you have to be willing to crash.
