Diesel vans may emit up to six times more toxic pollutants than is allowed under European limits, according to a report published on Thursday (19 May) by the Netherlands Organisation for applied scientific research, TNO.

The institute carried out tests in 2014. It was the first time that real-world emissions of nitrogen oxides (NOx) by vans were measured on the road instead of in the laboratory. The publication of the report followed a freedom of information request by Dutch newspaper De Volkskrant.

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The publication also included for the first time brand names of tested vans, legally known as light commercial vehicles.

They tested 10 vans in the Euro 5 category, from seven different brands, and one in the latest Euro 6 category.

“Overall it is observed that NOx emissions of Euro 5 light commercial vehicles as measured under real-world conditions in the lab or on the road are significantly higher than the values measured on the type approval test or the limit applicable to that test,” TNO wrote.

Before cars are allowed to drive on European roads, they need to acquire a so-called type approval.

Part of the approval process is emissions tests in laboratories, which entered the public spotlight last year when it emerged Volkswagen (VW) had cheated those tests on a grand scale.

VW had used so-called defeat devices, which allowed a car to recognize it was being tested, and switch to a more clean mode.

TNO has developed its own test, the Smart Emission Measurement System (SEMS).

“In on-road testing using SEMS, Euro 5 light commercial vehicles emitted on average five to six time more NOx than the Euro 5 limit value of 235 respectively 280 mg/km that is demanded on the type approval test.”

The tested Euro 5 vans were of the following types: Peugeot Expert; VW Caddy; Ford Transit; VW Transporter; Mercedes Sprinter; Mercedes Vito; Opel Vivaro; Renault Trafic, Iveco Daily; and Peugeot Boxer. The Euro 6 van, which came out of the test below the limit, was a Mercedes Sprinter.

The TNO researchers were cautious not to draw bold conclusions from the test results.

“The tests performed by TNO are not intended nor suitable for enforcement purposes and are not suitable for identifying or claiming fraud or other vehicle-related irregularities in a technically and legally watertight way,” it said, adding that the report has no basis for concluding that illegal defeat devices were used.

“For each make or model, only a single vehicle or a small number of vehicles are tested, which means that it cannot be ruled out that the results correlate to the specific condition of the tested vehicles.”

More testing would be needed to prove wrongdoing by specific car manufacturers, the report added.

However, the researchers did note the results “seem to indicate that the trend of a growing difference between type-approval and real-world emissions continues, at least up to Euro 5”.

The main conclusion, they write, is that “subsequent lowering of the type approval emission limits between Euro 1 and Euro 5 by a factor of 5 has not led to substantial reductions of the NOx emissions of diesel passenger cars and vans on the road”.

The report is yet another piece of evidence underpinning the need to shift to the so-called real driving emissions tests, which will be mandatory for EU cars as of September next year.

But even then, actual emissions may still be higher than those in the on-road test results.

The test drivers were “instructed to drive moderately ... unlike the typical observations of Dutch road users who often see speeding vans and aggressive driving with vans”.

Commercial vans, used for delivering goods, spend on average more times in cities, and therefore have potentially more damage to health than passenger cars.

One of the reports' authors, Richard Smokers, is due to appear in front of the European Parliament's inquiry committee into the diesel emissions scandal, next Tuesday (24 May).