Too much NOx from trucks

A recent research project by the Dutch consultancy TNO has shown that real world NOx emissions from Euro V trucks in urban driving conditions are three times higher than previously expected and only marginally better than those of Euro III trucks, although the type approval limit value is 60 per cent lower (see figure). The Euro III emission standards were introduced in 2001, followed by Euro IV in 2006 and Euro V as from October 2008.

Most of the measurements involved trucks with selective catalytic reduction (SCR) after-treatment technology. So far only one Euro V truck with exhaust gas recirculation (EGR) technology has been tested. This truck also showed increased NOx emissions at lower speeds, but to a much lesser extent than the SCR equipped trucks.

In a letter to the three EU Commissioners for environment, industry and transport, Dutch officials express concern that this will make it harder to meet EU targets for nature conservation and health protection. It may also complicate member states’ ability to meet national emission ceilings for NOx and air quality limit values.

Rules for implementing EU vehicle emissions standards are being developed under comitology. The Euro standards are set on the basis of laboratory tests, and while these now appear to correspond reasonably well to conditions for motorway driving, they obviously do not match when driving in urban conditions.

In the letter the Dutch suggest that the European Commission should negotiate an agreement with lorry manufacturers to modify the calibration software of Euro V vehicles to better reflect actual driving conditions and to ensure lower emissions.

Regarding the forthcoming Euro VI standards, that will apply as from 2013, the Dutch suggestion is to require the use of portable measurement systems (PMS) to ensure in-service compliance.

Figure: Comparison between real-world NOx emissions and emission limit value equivalents for heavy duty vehicles of various Euro classes. Source: Dutch letter to EU commissioners (February 2010)

According to Jos Dings, director of the green group Transport & Environment (T&E), the Dutch proposals are the best solution given the Euro V standards are already set in law and the vehicle type approval system cannot be changed because the EU is in transition from a European to an international system.

Christer Ågren


Sources: On-road NOx emissions of Euro-V trucks (December 2009), TNO report MON-RPT-033-DTS-2009-03840; Letter from the Dutch Ministry of Environment to Environment Commissioner Potocnik (February 2010); ENDS Europe Daily, 10 March 2010.

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