For month, the ongoing violation of EU limit values for nitric oxides in major German cities has been disputed in Germany. Since 2010, an annual limit of 40 μg/m³ for the protection of human health has to be observed in accordance with the EU Directive 2008/50/EC. Moreover, hourly values of 200μg / m3 may not be exceeded more than 18 times a calendar year. In some cities, it has not yet been possible to comply with the limit values with the implementation of air pollution control plans.
It was only at the end of July that the Federal Administrative Court in Stuttgart, after an action by the environmental NGO German Environmental Aid (DUH), asked the authorities of Baden-Württemberg to revise the air pollution control plans for Stuttgart and demand temporary driving bans as a measure against exceeding limits. The DUH also wants to initiate diesel driving bans in a further 45 municipalities.
At the beginning of the year, Germanys Federal Ministry of the Environment also demanded to only allow vehicles with a “blue badge” in environmental traffic zones where air quality limits are not met. This mainly affects Euro 6 diesel vehicles and petrol engine vehicles according to Euro Norm 3. This effectively means that environmental zones will be closed for a large proportion of diesel cars registered in Germany. Is this drastic measure really the appropriate solution to the problem?
Last year, a violation of the limit values was measured at 60 of the traffic-related air quality measuring stations in urban areas. NOx is the abbreviation of the two nitrogen compounds nitric oxide (NO) and nitrogen dioxides (NO2). In the combustion of fuel in the engine, NOx is produced as nitric oxide (NO). NO oxidizes to NO2, both in exhaust after-treatment and in ambient air. Diesel vehicles are considered particularly problematic with regard to NOx emissions.
According to the German Association of Cities (DStGB), they produce about 75 percent of the NOx emissions from road traffic. Newer Euro4/5 cars are no exception. These vehicles do not have any NOx secondary filter systems. Diesel cars conforming to Euro 5 standard produce lots of NO2 in order to remove particulate matter emissions in the particulate filter. The first generation of the Euro 6 vehicles also emit a multiple of the legally certified limit of 80 mg/km on the road. Only Euro 6 vehicles of the latest generation (Euro 6D), which will be launched on the market in autumn, will comply with the strict legal limits.
A driving ban would currently hit the majority of the 15 million diesel cars on German roads. This means a considerable restriction in mobility for affected vehicle owners, not only within driving ban zones, but also in traffic throughout the city. Retrofitting with SCR catalysts could provide a remedy but is only rarely possible in cases where the expense is acceptable. Software updates to Euro 5 and Euro 6 diesel cars announced at the “Diesel Summit”, a meeting between government representatives and representatives of the German car industry, alone would not be sufficient to comply with the air pollution limit-values in affected areas, according to the Federal Environmental Agency. Even in the case of new purchases of low-emission Euro class 6 A/B/D vehicles, there would be no guarantee for vehicle owners that they would not be included in future driving bans.
Few families or commercial operations can afford to purchase a vehicle in the most advanced pollution class in such a short term. Even with the repurchase of older diesel cars, which is currently being offered by many car suppliers in Germany, there are still high costs for buying new cars for consumers. Although there may be a few windfall effects, an increase in prices of new cars due to additional demand cannot be ruled out. Hardly any vehicle supplier could thus increase their production capacities in such a way as to meet the rise in demand fast enough.
The German Federal Environment Agency however, questions whether these vehicle-related measures can eliminate the problem of exceeding NO2-limits. From a macroeconomic perspective, one-sided measures to reduce NOx in diesel cars are questionable. Protection of the environment and resources are similarly not best served when the operating life of vehicle fleets is artificially shortened by driving bans. For these reasons there are strong doubts about the proportionality of a diesel driving ban in the environmental traffic zones.
In addition, car traffic in the immediate vicinity of inner city measurement points is not the only cause of limit value violations. In fact, universal urban traffic, industrial emissions and exhaust fumes from heating systems also contribute to urban and large-scale background pollution.
According to analysis carried out by the Federal Environmental Agency, emissions in the large-scale and urban background make up an average of half of the measured NO2 concentration at Berlin pollution points (Federal Environmental Agency 2014). In fact, in nationwide urban areas, background emissions of NO2 during the past year were measured as half as high as those at traffic-related measuring points (Federal Environmental Agency 2017). When local road traffic is added as a source of emissions, particularly in badly aerated streets, the concentration of air pollutants may be considerably excessive. This is due not only to diesel cars, but also to small vans, lorries and buses, as well as heavily motorized petrol-driven cars.
A 2016 survey of the real emissions of city buses from the municipal utilities of the German city Osnabruck shows, for example, that the NOx emissions of public buses can exceed the emissions of diesel cars by ten times or more. The emissions of older trucks of the Euro 5 standard are also clearly higher than those of cars with diesel engines. However, NO2 is not only emitted directly from vehicles but is also produced by chemical reactions of nitric oxide and ozone in the air, which affect a variety of external factors. The effect of a driving ban on diesel cars should therefore not be overestimated at these hotspots.
In the case of demands for driving bans, consideration must also be given to what has already been achieved in the past without taking such drastic measures. The transport sector has reduced NO2 emissions more than all other sectors. In 2015 emissions were only half as much as 15 years earlier, although the share of diesel cars in the stock of passenger cars increased enormously. Whereas 24 per cent of all passenger cars were powered by diesel engines in 2008, there were already 33 per cent (Federal Motor Transport Authority 2017) in the first half of this year. The volume of diesel cars has increased from 10 million to 15 million. There have also been changes reflected in traffic measuring stations. While the proportion of traffic monitoring stations reporting excess limit values rose to 70 per cent by 2011, only barely 60 per cent of the measuring stations were affected by limit excesses in 2016.
Five years ago, the median of the value of the exceeded limit was 10 µg/m3, last year it was only 7 µg/m3. Maximum values have also declined. When up to 120 µg/m3 were measured ten years ago at specific stress points, the highest figure in 2016 was 82 µg/m3. The same applies to the number of hours in which 200 μg/m3 has been exceeded. A few years ago, the limit value at some measuring points was exceeded by several hundred hours, last year the maximum was 35 hours.
Everything suggests that the implementation of local air pollution plans and autonomous generation updates to the vehicle fleet are already bearing fruit and that we are over the worst with regard to NOx emissions. In just a few years, the majority of diesel cars will also meet the demanding Euro 6 standard in actual driving conditions, which will further reduce the frequency and extent of limit value excess.
In general, it is more sensible to start with the effect of less costly and restrictive emission reduction options, before massively encroaching on the rights of citizens. The previously mentioned software updates from vehicle manufacturers are a cost-effective start. The automotive industry will also accelerate the technological change to more low-emission vehicles by means of its re-purchase operation. With the help of environmentally-oriented traffic control, traffic can be directed, redirected and made to flow in many places.
As a result, less traffic and a low-emission driving system would be achievable both at hotspots and in city centres. In addition, the promotion of public transport could make the use of bus and train more attractive than using private cars. Furthermore, a shift in heavy-duty traffic from the inner city or modernization of bus fleets also promise a significant emission reduction at a lower cost. Finally, it would have to be examined whether emissions from industry and heating systems could be reduced at a reasonable cost.
An open political discussion on the air pollution limit values for fine particles and nitrogen oxides should follow. Ultimately, the tightening of fine particle limit values led to the introduction of diesel engines, which mit less particles but more NO2. While most of the fine particles are of natural origin, due for example to tire abrasion and turbulence caused by road traffic, exhaust gases contribute only a maximum of 10 percent to the emission load.
Although this target conflict between fine particles and nitric oxide emissions is now regarded as technically solved, it makes engines more expensive and increases fuel consumption. Less demanding requirements for particulate emissions from passenger car engines could reduce the technical outlay for compliance with nitric oxide emissions without having a significant effect on the fine particle pollution of road traffic.
However, regarding the exceeding of NO2 limits, more rationality should return to the debate. Horror figures concerning premature deaths and loss of life due to increased NO2 concentrations are making the rounds but are comparatively less resilient. A causal relationship between NO2 concentrations and respiratory irritation as well as an intensifying effect on pre-existing respiratory diseases has been demonstrated. There is however no clear correlation between an increase in cardiovascular disease and even the increase in mortality due to increased NO2 concentrations, as the US Environmental Protection Agency (EPA 2016) observed last year in a scientific reassessment of air pollution limits.
Due to the difficulty in conveying the differences between outdoor air and the workplace thresholds for NO2, there is a need for discussion. The workplace limit value for industry and trades is a multiple of the external air limit values. These limits are valid only for healthy workers at eight hours a day and for a maximum of 40 hours a week, but the discrepancy is still remarkable. When the EU limits are applied, NOx concentrations, at the level of the applicable guidelines for offices and private areas, result in the threat of driving bans on diesel road vehicles (Federal Environmental Agency 2017).
Everything suggests that the air pollution limits should be complied with calmly, with a sense of proportion and avoiding too costly measures. A carefree renouncement of comparatively low-consumption diesel engines makes the accessibility of the climate more difficult, especially as the available alternative drive alternatives are so far rather disappointing. Pure electric vehicles are expensive and disappoint the drivers with regard to their range, but they also raise doubts about their ecological balance.
The same applies to plug-in hybrids. These vehicles only keep their environmental promises on paper, as a recent test by the General German Automobile Association (ADAC) showed in real driving situations. The key to solving the ecological problems of transport lies in a policy that allows for technological innovation in a wide range of drive technologies and air-cleaning measures. Central planning and ideologically motivated activism, which reduce our prosperity, undermine technological know-how and threaten jobs, are clearly out of place.