When the Volkswagen diesel scandal broke out in 2015, a lot of attention was paid to how the cars contain the polluting nitrogen oxide (NOX) in dramatic overstepping of regulators’ standards during real-world driving. But that wasn’t what ultimately landed VW Group in trouble with officials from the US Environmental Protection Agency (EPA) and European Union regulators. The main problem was that diesel VWs, Audis, and even Porsches contained secret “defeat tools,” or lines of code, in the car’s software that regulators knew nothing about. This code allowed the diesel cars to run cleaner in a laboratory than on the road.
In most cases, regulators know that vehicles will run dirtier in some real-world driving conditions than they did in the lab tests. They also know that lab tests are designed narrowly enough for automakers to exploit. Regulators in the US don’t uniformly test emissions under real-world conditions (although the EPA did a review of diesel vehicles after the VW Group scandal).
A new study published in Nature has now calculated the effect of lax regulatory practices and comes up with a body count – 38,000 people around the world died prematurely in 2015 due to excess particulate matter (including NOX) and ozone emissions from diesel vehicles.
Consequences in the real world
In the US, the federal emissions test of light vehicles (including passenger cars and some small commercial trucks) involves a 31-minute test where an engine is connected to a dynamometer in a laboratory. The test leaders study the exhaust emissions from a cold start, then while the car is running and finally after a warm start. There is scope for a carmaker to pass such a test without using secret software to turn its emissions control system on and off, as Volkswagen did.
In 2015, Ars spoke to a University of Colorado Denver researcher about the emissions compliance test. He noted that test conditions are well known to automakers before the day of the test, and manufacturers will go so far as to hire drivers who can most efficiently “drive” the car while it is hooked up to lab equipment to get the lowest test results. produce. emissions possible. Since the amount of emissions a car emits can be variable, regulators know that many diesels that meet the extremely narrow requirements of the EPA lab test produce emissions in excess of what is allowed, while a real driver would, for example, drive a steep incline or drive at low temperatures.
The lax emissions testing is not unique to the US: the authors of the Nature paper looked at 11 major car markets, including the US, the 28 member states of the European Union, Australia, Brazil, Canada, China, India, Japan, Mexico, Russia and South Korea. Together, those regions represent 80 percent of the diesel vehicle market. Tracking historical data on heavy and light diesel vehicle sales around the world allowed the authors to compile “emission inventories”. They compared that data with emissions data from more than 30 studies based on modeling and real-world testing of cars in the US, Europe, China and Japan.
The authors found that “nearly one-third of on-road heavy duty diesel vehicle emissions and more than half of on-road light duty diesel vehicle emissions exceed certification limits.”
Similar studies have been done to quantify the effects of the Volkswagen scandal in the US alone. In an October 2015 paper in Environmental research lettersresearchers determined that the additional emissions from the nearly 500,000 diesel VWs and Audis sold in the US would cause about 60 premature deaths.
This recent study is broader in scope: it covers a larger proportion of the estimated 4.4 million premature deaths from air pollution in 2015.
Fortunately, there is a way to prevent more premature deaths, and that means introducing emissions regulations already promulgated by the US and EU. In the years since Volkswagen was caught blatantly cheating to meet the minimum testing requirement, regulators have taken action to make emissions testing more rigorous. From this year, EU regulators will require vehicles to meet certain emission standards during real driving tests.
“Adopting and enforcing next-generation standards…could all but eliminate true diesel-related NOX emissions in these markets,” the researchers wrote, adding that by 2040, the stricter standards could help prevent about 174,000 deaths worldwide.
Critics might argue that if automakers can’t meet emissions standards without making cuts now, they might not be able to do it when standards are even stricter. But the authors noted that recent tests showed “real-world NOX emissions in accordance with certification limits are technically feasible.”
Nature2017. DOI: doi:10.1038/nature22086 (About DOIs).