New study on air quality from AVISO, Graz University and ifeu
At present infringement proceedings for exceedances of air quality limit values are pending against a whole series of EU countries – including Germany. Diesel vehicles are a relevant factor for air quality, although not the only one.
Diesel passenger cars virtually stopped emitting particulates several years ago thanks to powerful particulate filters. While a modern clean diesel (Euro 6 vehicle) has particulate emissions of almost zero, those from much older diesel passenger cars are still high. Therefore these vehicles are not allowed to enter the environmental zones of many towns and cities.
Nitrogen oxide (NOx) emissions from German road traffic have fallen by more than 70 percent since 1990 – despite the total volume of traffic increasing by around half from 1990 to the present day. According the German Environment Agency (UBA), diesel passenger cars are responsible for around one tenth of nitrogen oxide emissions in Germany. The values can be higher at measuring stations directly adjacent to roads.
The latest generation of Euro 6 vehicles reduces NOx emissions and improves the air quality. Modern diesel technology is a key solution to the air quality challenge. Another significant decrease will result from the Real Driving Emissions (RDE) testing procedure that will be the first to measure and limit the pollutant emissions from newly registered vehicle models on the road. Effective cleaning of the air will require rapid market penetration by the new technologies.
These are the main results of a recent study conducted by the Aachen research company AVISO in cooperation with the Graz University of Technology and ifeu (the Institute for Energy and Environmental Research) in Heidelberg. The study was commissioned by the German Association of the Automotive Industry (VDA). In coordination with the German ministries for the environment (BMUB) and transport (BMVI), the German Environment Agency (UBA) and the Federal Highway Research Institute (BASt), three measuring points in Germany were investigated, including the one with the highest values anywhere in the country – at Neckartor in Stuttgart. Based on forecasts for the size of the fleet from ifeu and on real emission factors from Graz University, AVISO calculated the trends in emissions and air quality at the measuring points.
The study concluded that the exceedances of air quality limit values were being mitigated by the increasing market penetration of Euro 6 vehicles and RDE. The “natural” fleet replacement will reduce the concentration of NOx in the air by 17 percent by 2020, which means that measuring points with an annual mean of 48 μg/m³ today will reach the limit value of 40 μg/m³ simply through vehicle replacement. That will bring 33 of the 72 measuring stations with exceedances back under the target.
Modern Euro 6 diesels are clean and efficient. Compared with their predecessors, they reduce the output of NOx both in relation to the limit value and on the road by about two thirds. The nitrogen oxide emissions from one of today’s diesels are around 98 percent lower than those at the beginning of the 1990s. In the period from 2000 up to today’s Euro 6 standard, NOx emissions from diesel passenger cars in the testing cycle have been reduced by 84 percent thanks to clean diesel technology.
The VDA continues to call for measures to improve the flow of traffic and prevent congestion. They can be implemented quickly and have a large effect: according to studies by the ADAC and the TUM (technical university of Munich), an “intelligent green wave” and a smooth traffic flow have the potential to bring down NOx values by almost one third. That would enable all the measuring stations that currently record an annual average of up to 57 µg/m³ to comply with the EU’s annual limit value.
Furthermore, buses and taxis in the urban traffic should be replaced with the most advanced vehicles. The currently limited number of modern vehicles, the high average age and the high urban mileages make major contributions to exceedances of NOx limit values.
The VDA is working toward the right mix of modern exhaust treatment, rapid fleet renewal and traffic-based measures to bring about an effective improvement in the air quality in towns and cities.
The most important results from the study by AVISO, Graz University and ifeu can be found on the Internet, at: https://www.vda.de/de/services/Publikationen/no2-air-quality-scenario.html.