Scientists have uncovered the mechanism inside cars that allowed German automaker Volkswagen to circumvent US and European emission tests using computer codes. The mechanism was used by Volkswagen over at least six years before the US Environmental Protection Agency (EPA) put the company on notice in 2015 for violating the Clean Air Act, researchers said.
During a year-long investigation, researchers led by Kirill Levchenko from the University of California San Diego in the US found the code that allowed a car's onboard computer to determine that the vehicle was undergoing an emissions test. The computer then activated the car's emission-curbing systems, reducing the number of pollutants emitted. Once the computer determined that the test was over, these systems were deactivated. When the emissions-curbing system was not running, cars emitted up to 40 times the amount of nitrogen oxides allowed under EPA regulations.
"We were able to find the smoking gun. We found the system and how it was used," Levchenko said.
Scientists obtained copies of the code running on Volkswagen onboard computers from the company's own maintenance website and from forums run by car enthusiasts. The code was running on a wide range of models, including the Jetta, Golf and Passat, as well as Audi's A and Q series.
"We found evidence of the fraud right there in public view," Levchenko said.
During emissions standards tests, cars are placed on a chassis equipped with a dynamometer, which measures the power output of the engine. The vehicle follows a precisely defined speed profile that tries to mimic real driving on an urban route with frequent stops. The conditions of the test are both standardised and public. This essentially makes it possible for manufacturers to intentionally alter the behaviour of their vehicles during the test cycle.
The code found in Volkswagen vehicles checks for a number of conditions associated with a driving test, such as distance, speed and even the position of the wheel, researchers said. If the conditions are met, the code directs the onboard computer to activate emissions-curbing mechanism when those conditions were met.
Levchenko, Professor Stefan Savage from UC San Diego and their team examined 900 versions of the code and found that 400 of that included information to circumvent emissions tests. A specific piece of code was labelled as the "acoustic condition" - ostensibly, a way to control the sound the engine makes. However, in reality, the label became a euphemism for conditions occurring during an emissions test. The code allowed for as many as 10 different profiles for potential tests.
When the computer determined the car was undergoing a test, it activated emissions-curbing systems, which reduced the amount of nitrogen oxide emitted. "The Volkswagen defeat device is arguably the most complex in automotive history," Levchenko said.
Researchers found a less sophisticated circumventing ploy for the Fiat 500X. That car's onboard computer simply allows its emissions-curbing system to run for the first 26 minutes and 40 seconds after the engine starts - roughly the duration of many emissions tests.
The study draws attention to the regulatory challenges of verifying software-controlled systems that may try to hide their behaviour and calls for a new breed of techniques that work in an adversarial setting.
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