DETROIT: The US Environmental Protection Agency (EPA) plans sweeping changes to the way it tests for diesel emissions after getting duped by clandestine software in Volkswagen cars for seven years.

Chris Grundler, head of the EPA’s office of transportation and air quality, indicated the agency would add on-road testing to its regimen. VW’s sophisticated software allowed its cars to pass tests in the lab and then spew pollution into the atmosphere while on the highway.

The revelations meant unwanted scrutiny for the EPA. Its testing procedures have been criticised for being predictable and outdated, making it relatively easy for VW to cheat. What’s more, the EPA did not initially uncover the problem; researchers at West Virginia University did, using on-road testing.

Grundler says the changes are designed to detect software and other methods automakers might use to rig a test.

The EPA and the California Air Resources Board (CARB) have engineers who are ‘developing clever ways in which these things can be detected’, Grundler says. He also notes that testing of diesel engines, which make up only one per cent of the vehicles on US roads, wasn’t the top priority for the EPA. The agency did have on-road testing equipment — but it was assigned to monitor automaker gas mileage estimates and heavy-duty diesel trucks, where cheating had been uncovered in the past.

Grundler, who has been with the EPA for more than three decades, says the lack of on-road testing for diesels ‘might change in the future’. An announcement of the changes could come today. VW has admitted to installing software on Volkswagen and Audi cars with four-cylinder diesel engines that switches on pollution controls when they are being tested. When the software, called a ‘defeat device’, determines that the cars are back on real roads, the controls are turned off. The EPA says about 500,000 US cars, including the Jetta, Golf, Beetle, Passat and Audi A3 have the cheating software, and VW says a total of 11 million cars have it worldwide.

VW was able to fool the EPA because the agency only tested the cars on treadmill-like devices called dynamometers and didn’t use portable test equipment on real roads. The software in the cars’ engine-control computers checked the speed, steering wheel position, air pressure and other factors to determine when dynamometer tests were underway. It then turned on pollution controls that reduced the output of nitrogen oxide, an ingredient in harmful ozone, EPA has said.