All the diesel vehicles tested by the UK government exceeded emissions limits in real driving conditions, but it found no evidence of car manufacturers, apart from the VW Group, fitting devices to defeat the approved emissions test programme.

Today (21 April) the UK government published its research into emissions levels from leading diesel car models, as part of its investigation into potential manipulation of emission controls.

Tests were carried out on a total of 56 different vehicle types in Germany and 37 different vehicle types in the UK, over a period of six months.

In an independent assessment, published as part of the report, Professor Ricardo Martinez-Botas, head of thermofluids division, Mechanical Engineering Department, Imperial College London, said: “It is clear from the results that a large gap exists between the regulated nitrogen oxide (NOx) emissions measured under controlled laboratory conditions and on-the-road performance.

“Future testing regulations will include a real driving emissions (RDE) testing element as part of the procedure for approval, and the tests in the laboratory setting will be more representative, with the new worldwide harmonised light duty vehicles test procedure (WLTP) replacing the NEDC. Both these measures aim to reduce the emissions gap.

“Vigilance will be needed to ensure that the gap does not grow again over time, as we know that higher NOx emissions in the real world lead to a substantial health impact to society.”

Transport minister Patrick McLoughlin, commented: “Our tests published today have not detected evidence of manipulation of emissions lab tests as used by the VW Group by any other car manufacturer.

“The tests do show the widespread use of engine management systems to prevent engine damage which can lead to higher emissions in real world temperature conditions cooler than those in the approved lab test.

“The UK has been leading in Europe in pushing for real world emissions tests which will address this problem. Real world tests will be introduced next year to reduce harmful emissions, improve air quality and give consumers confidence in the performance of their cars.

“Following the Volkswagen emissions scandal the whole of the automotive industry must work hard to restore public trust by being transparent about the systems they employ and advancing plans for introducing cleaner engine technology.”

In an independent assessment, published as part of the report, Professor Ricardo Martinez-Botas, head of thermofluids division, Mechanical Engineering Department, Imperial College London, said: “It is clear from the results that a large gap exists between the regulated nitrogen oxide (NOx) emissions measured under controlled laboratory conditions and on-the-road performance.

“Future testing regulations will include a real driving emissions (RDE) testing element as part of the procedure for approval, and the tests in the laboratory setting will be more representative, with the new worldwide harmonised light duty vehicles test procedure (WLTP) replacing the NEDC. Both these measures aim to reduce the emissions gap.

“Vigilance will be needed to ensure that the gap does not grow again over time, as we know that higher NOx emissions in the real world lead to a substantial health impact to society.”