Revelations that Volkswagen, the world’s biggest car maker, rigged its emissions testing in the United States to circumvent regulations and boost its sales have sent shock waves through the car industry. On September 22, the company admitted that it had used special software to lower emissions during laboratory tests of some of its diesel vehicles; on September 23, its chief executive, Martin Winterkorn, resigned.
The firm's admission suggests that about half a million cars on US roads and 11 million worldwide may be emitting substantially higher levels of nitric oxide and nitrogen dioxide (collectively known as nitrogen oxides or NOx) than expected from lab tests. The implications for human health are unclear, and some think that the scandal could yet spread to other car makers. Experts have long been aware, however, that lab tests often greatly underestimate actual emissions from diesel cars.
How did the manipulations come to light?
The tests found that the levels of NOx emitted by a Volkswagen Jetta were 15–35 times greater than dictated by the US standard (31 milligrams per kilometer), depending on road and driving conditions. Likewise, those for a Volkswagen Passat were 5–20 times greater. The BMW X5, however, remained at or below the standard except during rural uphill driving.
The findings prompted the US Environmental Protection Agency (EPA) to launch investigations into Volkswagen tests in the United States. The EPA also threatened to withdraw its approval for all Volkswagen diesel vehicles approved for sale there; Volkswagen responded by admitting that it had tricked emissions tests by using software that senses when the car is being tested, and switches on full emissions control.
Why are diesel emissions worrying?
In London, where more than 3,000 deaths a year are attributable to air pollution, diesel road traffic is responsible for 40% of NOx emissions. Across the European Union, some 20% of the urban population is estimated to live in areas where nitrogen-dioxide concentrations exceed air-quality standards.
What problems with emissions testing were known before Volkswagen's admission?
In 2011, scientists with the European Commission’s Joint Research Centre (JRC) in Ispra, Italy, reported that average on-road emissions of tested diesel vehicles exceed allowed limits by up to 14 times. By contrast, NOx emissions of petrol vehicles stayed within the limits.
A year later, the JRC compared NOx emissions of a diesel passenger car that was made to comply with emissions standards due to be implemented in 2014 — called Euro 6 — with six older-type cars. Thanks to its advanced catalytic converter, the new car type did perform considerably better, but on the road it still exceeded the existing emissions standard by about 260%.
And an analysis last October by the ICCT of real-world emissions by 15 modern diesel cars — twelve certified to the EU standard and three to the equivalent US standard — found that although some cars performed reasonably well, others had real-world emissions up to 25 times higher than the 80 milligrams per kilometer allowed by the Euro 6 regulation. The average level of NOx emissions was about seven times higher than allowed in the EU.
Is Volkswagen alone in deploying software designed to circumvent tests?Transport & Environment study, released earlier this month, that found that Volkswagen was just one of many companies with diesel vehicles whose on-the-road emissions were above the limits. However, the study did not look for evidence of trickery, and was confined to Europe, where diesel emissions standards are less stringent and where Volkswagen itself has not admitted using the software in tests.
What is happening now?
Will that solve the problem?
What does the scandal mean for the future of diesel in cars?
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