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emissions of every car on the road.

“Since 2011 we’ve been publishing

results showing that diesel cars in real

driving were emitting high amounts of

nitrogen oxides,” he says.

His methodology is dramatically

different to the official tests. It involves

setting up a ‘sensing beam’ across a

major road. “When vehicles drive

through it, it makes a measurement of

each individual vehicle,” he explains.

“Then we record the number plate of

the vehicle, the vehicle’s speed and

acceleration, and we cross-reference the

number plate to the vehicle registration

database in the UK.”

By the end of 2015, he’d collected

data on as many as 70,000 individual

cars, allowing him to generate

statistically-rigorous averages of real-

world emissions data on all of the most

popular models of car out there. His

results show that it’s not just Volkswagen

failing to meet the emissions standards

under real-world conditions. “Basically,

you see that all manufacturers are at a

staggeringly similar level. Very similar,”

he says. “It’s very easy to collect an

awful lot of driving information. The

[European] test is hideously out of date,

and ineffective.”

CHOKING PROBLEM

Prof Håkan Pleijel at the University of

Gothenburg is a specialist in the effects of

air pollution on vegetation. He agrees that

the test needs revamping. “These test

cycles don’t really correspond to the way

the engine would work when it’s out

driving in the city,” he says. “There is

space for improvement in terms of using

“NOx levels have declined to some extent in

Europe over the last few decades,” says

Pleijel. “But in some cases the decline does

not match the expected emission reductions.

It would be expected that the concentrations

would have gone down a bit further.”

That’s the reason why many European

cities are failing to meet air quality standards.

When the European Environment Agency

(EEA) last published data in 2014, more than

95 per cent of the urban population was

exposed to unsafe levels of certain pollutants.

“That leads to high costs,” explained Hans

Bruyninckx, EEA’s Executive Director, at

PHOTO: GETTY, ALAMY the time. “For our natural systems, our

Prof Håkan Pleijel, University of Gothenburg

“NOX LEVELS HAVE DECLINED

TO SOME EXTENT IN EUROPE.

BUT IN SOME CASES THE

DECLINE DOES NOT MATCH

THE EXPECTED EMISSION

REDUCTIONS”

0.0

0.5

1.0

1.5

2.0

2000 Year of registration 2005 2010

Euro 3 Euro 4 Euro 5

more realistic test cycles or testing the cars

actually driving in ordinary traffic.”

The obvious result of this f lawed testing

methodology means that there’s far more

pollution being emitted than we realise.

NOx Emissions by Source

500

0

1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020

1,000

1,500

2,000

3,000

2,500

Other Road transport

Domestic

Source: Dr James Tate

Power stations

Non-road Industry

transport and

machineryneryy

ranspo

machin

Year

Graphical analysis

According to analysis by the Institute for Transport Studies, cars have not been meeting the emissions

standards set by Europe outside the test lab. However, overall emissions from various sources appear to

be falling and the growth of alternative fuels may help improve this further

NOx emissions by manufacturer and year of first registration

Audi Peugeot

BMW Skoda

Ford Vauxhall

Land Rover Volkswagen

Mercedes Volvo

NOx emissions (grams per km)

NOx emissions (kilotonnes)

SCIENCE