Carmakers in Europe, Asia, and North America have met exhaust emission limits for decades, as measured by strict standardized vehicle tests on dynamometers, or "rolling roads."

With the Volkswagen diesel scandal now entering its third week, U.S. and European regulators plan to test more cars under real-world conditions to measure their on-road emissions.

If that happens, European makers say, the legal limits for emissions of nitrous oxides, or NOx--the very substance that VW's diesel TDI cars cheated on--must be raised significantly.

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In fact, they say, those limits must rise 70 percent from today's levels--which all those makers have achieved on the static tests. While they apply to diesel and gasoline engines, they're much tougher for diesels to meet.

The startling demand came in the form of a letter last week from the European Automobile Manufacturers Association, which includes Volkswagen, along with BMW, Daimler, Ford, General Motors, Hyundai, PSA Peugeot Citroën, Renault, and Toyota.

Reported late last week in auto-industry outlets, The New York Times, and elsewhere, the letter was not confirmed by the association, which said it would wait to respond to final proposals for updated emissions tests.

2016 Volkswagen Beetle TDI Convertible

2016 Volkswagen Beetle TDI Convertible

But the letter largely concedes, as the Times writes, that automakers "cannot meet pollution regulations when cars are taken out of testing laboratories."

Indeed, draft proposals suggested a 30-percent rise in permissible NOx, reportedly countered by the association with the 70-percent figure.

European emission tests are even more divorced from real-world driving conditions than their U.S. equivalents. Carmakers may remove door mirrors and tape over body seams to improve aerodynamics, for instance.

ALSO SEE: Why Did Volkswagen Cheat On Diesel Emissions In Its TDI Cars?

Drivers in Europe complain of real-world fuel efficiency as much as 30 percent lower than ratings. Similarly, tests last year proved that on-road emissions were far higher than those recorded on the dynamometer tests.

A proposal for more realistic testing has been grinding its way through the European Union approval process, with Europe's automakers proposing to soften, extend, or delay it.

Now the VW scandal has brought the issue of test results versus real-world driving emissions to the forefront.

2011 BMW 335d sedan

2011 BMW 335d sedan

And the news was already dire for Europe's automakers.

Last year, the International Council on Clean Transportation (ICCT)  tested several so-called "clean diesel" vehicles to see if they complied with new and tougher Euro 6 emission limits--roughly equivalent to those in place in the U.S. since 2008.

Its report notes that not all tested vehicles were out of compliance: "Some of the tested vehicles had average emissions below Euro 6 emission limits."

MORE: Are 'Clean Diesels' Actually Not Nearly As Clean As Claimed? (Apr 2015)

But most did not: "On average, real-world NOx emissions from the tested vehicles were about seven times higher than the limits set by the Euro 6 standard," the group wrote.

It concluded that excess emissions "were due to transient increases in engine load typical of everyday driving (e.g., going up a slight incline), or to normal regeneration events in the normal diesel exhaust aftertreatment systems."

With the fallout from the Volkswagen diesel scandal still reverberating, European makers are caught between a rock and a hard place.

'Diesel fuel only' caution on Audi Q7 TDI

'Diesel fuel only' caution on Audi Q7 TDI

They know that many of their vehicles are grossly out of compliance with the limits they all met whenever those cars are taken off dynamometers and actually used on real roads by live human drivers.

But with public anger at VW's blatant cheating still swirling, and numerous investigations all over the globe focusing on the industry's compliance at large, they have no good alternative.

So the suggested 70-percent boost in legal NOx limits can be seen not as an audacious and self-centered demand, but a desperate plea for the only solution they have that lets them legally comply under real-world conditions.

Good luck with that.


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