Testing vehicle emissions in the laboratory is a way to guarantee identical procedures, but it doesn't exactly mimic the results from an on-the-road drive. Ford, for example, famously had a problem with dynamometer testing in the Total Road Load Horsepower (TRLHP) calculations for the C-Max Hybrid. Over in Europe, the authorities are considering new rules that will not affect the emissions levels that need to be reached (those are already in process) but how the vehicles will be tested. Reuters doesn't name the new rule, but we think it could be connected to the UN-supported World Light Vehicle Test Procedure (WLTP), which emphasizes actual driving results over lab numbers.
A new draft legislation is making the rounds that would force the tests to be done on, you know, actual roads instead of in labs/ You can probably guess the reasons why. Reuters calls the problems one of "loopholes," but whatever name we apply, the problem is that the official figures and reality don't match. An unnamed EU official told Reuters, "In the real world we have seen that NOX emissions are higher than indicated by the test, up to a factor 4 or 5 and exceptionally more." This is not a new issue. Back in 2011, the group Transport And Environment said that the CO2 emissions numbers claimed by automakers are "less and less a reflection of what we are seeing on the road." You probably won't be surprised to hear that, while the auto industry admits the lab tests aren't accurate, it doesn't just want to accept a new test procedure mandate. The VDA, a lobbying organization for the German automakers, is working on its own proposal for real-world tests.