Today has not been a great day for diesel vehicles. First, Volkswagen finally came to an agreement in the US that involves buybacks, payoffs and an environmental compensation fund. Now, according to a UK Department for Transportation (DfT) study, every diesel it tested on the road managed to exceed regulatory limits. That's not gone well.
Over six months, DfT tested 37 diesel vehicles on the road. All of these cars passed muster when being tested in the lab, but once they hit the road, it was an entirely different story. In every vehicle it tested, on-road nitrogen oxide emissions were in excess of legal limits.
This isn't about defeat devices, though. In fact, the tests "have not detected evidence of test cycle manipulation strategies as used by the Volkswagen Group," according to a DfT statement. However, the tests do show that cars' computer systems are tweaking engine settings on the fly, partially to prevent engine damage, which can lead to higher emissions in varying temperatures. Earlier this year, Daimler claimed temperature fluctuations, among other factors, were to blame for high emissions in its diesel vehicles.
If anything, DfT's findings show that lab testing is wholly insufficient when it comes to figuring out actual environmental impact. To that end, the UK will roll out real-world testing procedures starting next year, in an attempt to examine a vehicle's true emissions. The US Environmental Protection Agency has already promised to institute real-world testing, and it's likely that other world governments will do the same in the coming years.