EPA now testing every new diesel on the road

It just got a little harder for cars to cheat the emissions testing system.

After discovering software in Volkswagen diesels that falsifies emissions levels, the United States Environmental Protection Agency confirmed Monday that it's now conducting on-road emissions tests for each and every diesel vehicle in the United States.

In years past, testing was done only in the laboratory, using a controlled "rolling road" in lieu of actual asphalt. VW was able to cheat emissions tests because its four-cylinder diesel vehicles knew when the car was in such an environment. On-road testing was previously limited to large trucks.

"The agency has expanded its testing of pre-production, production, and customer-owned vehicles to screen for defeat devices, " an agency representative said in an emailed statement, declining to reveal specific details on the testing procedures.

In other words, testing now extends to all 2015 and 2016 model year diesels and to any diesel that seeks EPA certification in the future, which should ensure that all automakers are adhering to pollution rules and regulations.

Volkswagen's vehicles were the first to be tested under this new regimen, and those tests uncovered emissions-related software also hiding in the automaker's six-cylinder diesel models.

It will take several weeks for every diesel to undergo on-road testing, according to The New York Times, which was first to confirm the expanded testing.

Back in September, Volkswagen admitted to using software tweaks to falsify nitrous-oxide emissions levels on approximately 480,000 vehicles in the US. The cheating is not limited to the US, either -- some 11 million vehicles worldwide contain this defeat-device software. The automaker has not yet unveiled its plan for fixing every affected model.

Volkswagen did not immediately return a request for comment.