The miseducation of the diesel car

Vehicle testing

I recently read an open letter in the Corriere della Sera by a VW engineer working on engine development and emissions (that’s what I call a hot seat!). The letter contains some pretty remarkable rationalizations of the use of defeat devices, going as far as to suggest that no one was really hurt by them (on just how wrong that notion is see here). For all its faults, I admit it made for quite an interesting read. Strangely enough, the bit that really captured my attention was this engineer’s candid, off-topic confession that she blows her nose in the car and throws the dirty tissues out the window while driving because she wasn’t told any better as a child. It struck me that this suggests a rather good metaphor for the whole issue of real-world diesel emissions in Europe: It’s all a matter of bad parenting! Too many years of weak standards (an unrealistically soft driving cycle, higher emission limits for diesel) and no real enforcement have turned the diesel car industry into an unruly teenager, and its loving parents (the European authorities and the EU member states) are having trouble keeping it in check.

On October 28, the preliminary details of an agreement reached by EU member states on the new Real-Driving Emissions (RDE) regulation regarding on-road emissions tests for passenger cars were announced, and they represent a significant retreat from what we’d expected it would require. The European Commission had initially proposed setting the on-road emissions limit for nitrogen oxides (NOx) emissions from diesel cars for 2017 at 1.6 times the laboratory test-based limit, then lowering it to 1.2 times for the second phase in 2019. During a meeting of the Technical Committee on Motor Vehicles, the emission allowance was increased from 1.6 to 2.1 times the laboratory test limit (from 1.2 to 1.5 for the second phase), and the introduction of the more stringent limit for the on-road tests was delayed until 2020. Furthermore, EU authorities opened the door to an additional layer of post-processing of the on-road emissions test results that would effectively lower the reported results. And all of this comes in the wake an emissions scandal of unprecedented scale! It’s akin to our rowdy teenager crashing daddy’s old car into a police station while intoxicated, then being told to drive mommy’s luxury car in the future because it’s safer.

The refusal to take a bolder stance on diesel NOx emissions is particularly unfortunate because the technologies that make diesel cars reasonably clean during real-world driving are already in production. That’s right, a minority of diesel cars sold in the EU are clean, already today. We have independent test results that confirm this for both on-road and laboratory measurements, and we’ve also seen that software modifications (of the good kind) could improve NOx emissions of current cars without significant tradeoffs. Our recent NOx control technology market survey also revealed that there are substantial differences in the hardware choices made by the different Euro 6 diesel car manufacturers present in the EU market (see figure). We even found one manufacturer (BMW) that equipped different NOx aftertreatment systems in the EU and the U.S. for the same model denominations for the model years 2012–2014. Our interpretation of this situation is that the more stringent Tier 2 emission standards (and the even more stringent Tier 3 standards starting in 2017) are driving the adoption of state-of-the-art NOx control solutions in the U.S., while European cars can get away with less robust technology. It appears that our unruly kid is actually quite well behaved when visiting with uncle Sam!

Market shares of NOX control technologies for diesel cars in the EU (Euro 6 standard) and US (Tier 2 standard)

The fact is, diesel cars are emitting far more NOx than they should because EU regulations have been too lenient for too long. The latest agreement reached by EU member states is a missed golden opportunity to address Europe’s air-quality problem by forcing the required technological adjustments to bring real emissions and legal limits in line. The VW scandal may have surfaced in the U.S., but the diesel emissions problem is very much a European affair. Diesel cars account for more than 50% of new passenger car registrations in the EU every year, compared with less than 1% in the U.S. And NOx emission limits for diesel cars were always less stringent in the EU than those for gasoline cars. Talk about applying a different set of rules for the favorite child!

Diesel car manufacturers might be celebrating the latest RDE deal. The European Commission and a handful of key member states—those parents, adept at finding excuses—may find enough reasons to say this is an acceptable compromise for all parties. But the ultimate fate of diesel cars in Europe will not be entirely decided behind closed doors in a Brussels meeting room. The acceptability of the compromise will have to be scrutinized by the European Parliament and the European Council in the coming days. France’s environment minister has called the RDE deal “unsatisfactory“. One hopes that more political leaders across EU will decide to take a similar stand and have something more to say. Like maybe, Hey kid! Pick up that tissue! We don’t behave like that around here!