High diesel NOx emissions ‘likely for decades’ due to failing tests

High levels of nitrogen oxides (NOx) in cities, caused by diesel cars, are likely to persist for decades, the UK Government was recently forced to admit. In evidence to the European Court of Justice, in a case brought by Client Earth, the government admitted it would be at least 2030 before London, Leeds and Birmingham meet nitrogen dioxide standards that should have been achieved in 2010.

The ‘Euro’ standards system of vehicle emissions limits was intended to tackle urban air pollution. But ‘real world’ NOx emissions from diesel cars have typically been three to five times higher than official test results. Now a report from Dutch consultancy TNO shows the new Euro 6 standard introduced at the start of 2014 is no better, with real-world levels being six times higher than the designated limit.
TNO, testing on behalf of the Dutch Ministry of Infrastructure and Environment, found that in spite of facing a tighter NOx emissions limit (80mg/km), Euro 6 vehicles produced around 500mg/km in real-world circumstances, and are approximately equal to Euro 4 and Euro 5 vehicles.
The Euro 6 results come as the Mayor of London announced plans to charge drivers of all diesel cars, except those that meet the Euro 6 standard, £10 (€12.60) to drive in the city centre. Mayor Boris Johnson will also lobby the UK government to raise road tax on diesel cars to encourage drivers to switch to less-polluting vehicles.
‘What the real-world testing shows is that Euro 6 cars are no better than previous standards in terms of pollution. London and other cities considering a diesel charge should not exempt any diesel cars, including Euro 6 vehicles,’ said Greg Archer of T&E. ‘City-centre charges and fuel and vehicle taxes should reflect the pollution that cars actually emit on the road.’
Part of the reason for the huge difference between a car’s performance in the real world and in a type approval test is that these tests are obsolete. Carmakers are able to circumvent the rules by programming the test car to recognise when it is being driven on the cycle and produce lower emissions.
There is even emerging evidence that some pollution abatement equipment is deliberately designed to not work properly. Urea, which is injected into the car exhaust to dispel harmful NOx emissions, is stored in a small bottle. For drivers’ convenience, carmakers manipulate the injection system so that urea is only used during certain periods of acceleration (which also, coincidently, correspond to moments of test-cycle acceleration). At all other times no urea is injected – so more harmful NOx emissions are released.
A new system of better real-world emissions tests was due to be introduced in 2012 but has been delayed through industry lobbying and arguments intended to weaken the new rules. For example, carmakers proposed tests should only be conducted in urban areas, despite the high levels of pollution produced by cars on motorways. Carmakers also want test cars to only be driven on known routes with trained and experienced drivers to minimise pollution. They also want tests to attach more weight to periods when the car is decelerating or stationary – when emissions are lower.
‘The delays to real-world driving emissions tests are contributing to hundreds of thousands of needless deaths. The weakening of proposed new test procedures casts significant doubt on whether the new system will ever be effective. Cities have no choice but to ban diesels and restrict vehicle access until tests can effectively distinguish between clean and polluting vehicles,’ Greg Archer concluded.
Air pollution in the EU causes more than 400,000 premature deaths each year. 
Sales of diesel cars have grown strongly in Europe from around one-third of new cars in 2000 to over half today. This is largely the result of generous tax breaks for diesel cars that have lower CO2 emissions. However, T&E research has demonstrated these test results are also distorted by carmakers.