All top diesel cars break real-world emission limits, tests find

All top-selling diesel cars tested as part of a UK inquiry following the Volkswagen emissions-cheating scandal have been found to produce higher levels of air pollution on the road than legally allowed under laboratory conditions.

Laboratory testing of car emissions has been found to be inadequate, DfT said

A report published by the Department for Transport (DfT) today (April 20) shows that not one of the 37 vehicle types tested over a six-month period met the legal nitrogen oxide (NOx) level of 180mg/km for Euro 5 cars and 80mg/km for Euro 6 cars when driven on the road.

The government said the results provided further evidence that NOx emissions are higher in real world conditions and on test tracks than they are in laboratory conditions, which are widely used to test vehicle pollution levels.

But, as existing lab tests have been shown to be inadequate, new real driving emissions (RDE) tests are being brought in throughout the EU next year to “improve consumer confidence in manufacturers”, according to DfT.

The tests were carried out as part of an inquiry into vehicle emissions set up in the wake of German carmaker VW’s admission in September 2015 that it had deliberately installed software to manipulate laboratory emission tests.

Labour MEP Seb Dance this week claimed an ongoing separate EU inquiry had found that authorities knew of the existence of these cheat devices as far back as 1998.

However, today’s report has found no evidence of ‘cheat software’ being used in any of the vehicles tested, except those of the Volkswagen Group.

According to the report, VW Group’s Skoda cars “showed how effective Volkswagen Group’s cycle recognition strategy was in detecting the laboratory conditions and altering the emissions to as to pass the test”.

DfT Euro 6 road test results (click to enlarge)

Test results

According to the report, on-the-road tests showed that all of the Euro 5-standard diesel cars tested were “substantially higher” than the 180mg/km type approval limit for  NOx (nitrogen oxides). The best performers were three times higher than the limit and the worst results as much as 10 times higher.

On-the-road tests for Euro 6-standard vehicles, meanwhile, showed emissions were on average over six times higher than the tighter 80mg/km official limit for this exhaust standard. The best results were less than twice the limit, while the worst performers were 12 times above the legal limit.

On average, Euro 6 diesel NOx emissions were six times higher than the legal limit. However, the limit for Euro 6 vehicles is much lower than Euro 5, and therefore the average emissions from Euro 6 cars were half that of the emissions from Euro 6 diesels.

Indeed, the track test emissions from Euro 6 vehicles were found to be over 70% lower than those for Euro 5.

DfT Euro 5 road test results (click to enlarge)

Department for Transport

Next month the UK government will present the findings of today’s research to the European Research for Mobile Emission Sources — the body responsible for collating vehicle emission data — in order to inform its updated emissions factors later this year.

Commenting on today’s report, Transport Secretary Patrick McLoughlin said: “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.

“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” – Transport Secretary

“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.”

An investigation by the German Ministry for Transport, which separately looked at 56 different vehicle types, was also carried out alongside the UK investigation.