(Image: Patrick Pleul/DPA/Press Association Images)
Volkswagen’son 22 September that many of its cars tricked their way through routine tailpipe emission tests could throw light on why many European countries have failed to meet targets for reducing pollution from airborne nitrogen oxides (NOx).
Failure to meet targets potentially means– the UK government estimated issued earlier this month that nitrogen dioxide emissions account for up to 23,500 premature deaths in the UK, mainly through heart and lung disease.
VW rigged the tests by fitting its cars with a “defeat device”, a component designed to recognise when the emissions test is under way and to distort the real-world performance of the engine so that the emissions fall within the limit.
Investigation by New Scientist suggest that while no other manufacturers of diesel vehicles will have gone as far as VW to cheat their way through the tests, there may be many that legally deploy unrealistic conditions during testing to artificially reduce strain on the engine, and with it the emissions produced.
The aim is to find a performance sweet spot that maximises the apparent fuel efficiency of the vehicle and minimises the apparent emission profile, even if both deviate from how the car would perform in the real world.
Strategies to reduce strain on the engine could include dropping the tyre pressure, turning off the air-conditioning and heating, or using a fully charged battery not connected to the car’s alternator, which also reduces fuel consumption.
“None are as extreme as what VW did, but there are 1001 tricks you can play to reduce emissions during the test,” saysof the University of York, UK. “The key is to accelerate as slowly and smoothly as possible to put the minimum load on the engine.”
“It’s clear that both the on-road fuel consumption and emissions from European cars can be significantly higher than the official vehicle test measurements would indicate,” says, head of the air pollution group at the European Environment Agency. “The amount of fuel cars use on the road can be 30 per cent or higher more than official measurements, and for NOx, the differences are even higher, particularly for diesel vehicles, with real-life measurements showing that emissions can be as much as four or five times higher than in the test.”
“There have been rumours that some vehicles ‘know’ they are being tested, but this is the first time it’s been confirmed,” says Adams.
If this practice is widespread, it could help to explain why NOx emissions in many European countries continue to overshoot targets (see map, below), becausein the region, according to the European Environment Agency.
Recent information gathered by the agency shows that EU member states have struggled to meet national limits for NOx set in European legislation, on the basis of what manufacturers said they could achieve technologically. By 2010, 11 of the 27 countries still hadn’t reached the target, and six still hadn’t by 2013, including France and Germany, the home of VW.
“In 2013, Germany and France reported the highest exceedances of NOx limits, with 218 kilotonnes and 180 kilotonnes respectively,”.
Growth in traffic
The two countries were also the major overshooters going back to 2010. Austria, Belgium, Ireland and Luxembourg have also been persistent over-polluters on NOx.
But Adams says we don’t know if strategies used by manufacturers to fool the testing system have contributed to the unexpected failure of countries to reach NOx targets.
The agency says that while unexpectedly large amounts of pollution from supposedly clean cars is one possibility, there are other explanations. One is the growth in overall traffic, and another the increase in cars that burn diesel instead of petrol. Diesel cars release less carbon dioxide than petrol cars, but the European Environment Agency estimates that diesel accounts for 80 per cent of total NOx emissions from cars.
Adams says new tests have been developed within Europe to more closely mimic real driving conditions. “The sooner they are in operation, the better,” he says. “They’ve been agreed and it’s now down to timing, so it could be as soon as 2017, or as late as 2021.”
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