The EPA plans to expand real-world testing on 2015 and 2016 model-year vehicles while performing more random, spot-testing for some older vehicles. Such testing involves either attaching special machines to the rear of the vehicle or putting them in the trunk. It's a more cumbersome method than lab testing and it has primarily been used for larger trucks, so far, but EPA folks say that will need to be expanded in the wake of the VW issue. The key is to be able to accurately measure the nitrogen oxide that diesel engines truly emit.
European regulators are also slated to move over to real-world testing procedures in 2017. All of this was spurred by the discovery that VW apparently installed so-called cheat software in as many as 11 million vehicles worldwide. The EPA said earlier this month that another 10,000 or so vehicles made by VW and its Audi and Porsche affiliates may also have the cheat software, though VW has disputed that finding. No other automakers have been found to have uses such software since the VW discovery.