Parameter estimates for NOx models were exponentiated and are presented as percentage differences from the geometric mean concentration of NOx.
Diesel cars must meet an official EU limit for NOx but are only tested in a laboratory under fixed conditions.
The Volvo spokesman said: "Every Volvo car on the market today meets the legal Euro 6 standard for NOx emissions, based on the current test".
"For NOx, [diesel] cars are on average four times over the legal limit, because of the lenient nature of the test cycle in the EU".
The EU standard for NOx levels is 40 micrograms per cubic metre (40 µg m-3) but many of our cities now outstrip acceptable safe levels.
From 2010 onward, all new truck engines must achieve tough, near-zero limits for NOx, a chief ingredient of smog.
Heterogeneous photocatalysis is a promising method for NOx abatement.
These features are also the same for NOx, PM10, and CO2.
Fig. 2 Different technologies available for NOx emissions reduction from Wik (2010).
Threshold exceedances (in %, red) according to the Gothenburg protocol for NOx emissions in 2010[19].
This value equals 7.91 g/l for CO and 0.64 g/km for NOX.
