And the pressure is growing. A few weeks ago the European Commission sent a second warning letter to the North Rhine Westphalia Environment Minister Johannes Remmel (Greens) and commenced an infringement procedure. Following a statement by the Ministry, Brussels will decide whether the EU will sue. It could result in fines, some of which communes will have to pay.

Under an EU regulation on the environment in force since 2010, the annual average level of nitrogen dioxide in the air may not exceed 40 micrograms per cubic metre. This upper level is exceeded in many cities, including Bonn. In 2016 the Dusseldorf administrative court held that the city of Dusseldorf must at least consider a driving ban in the city centre in its clean air plan, deciding in favour of Deutsche Umwelthilfe. The Cologne administrative court has to address a complaint against Bonn and Cologne about their clean air plans. According to a court spokesperson, the start of proceedings has been put on ice pending a judgement on a matter of principle by the federal administrative court.

But the need for action remains. The Cologne district government confirmed it had convened a project group for the Bonn clean air plan at the end of 2016. Dirk Schneemann, spokesman for the district government said: “Measures to reduce the nitrogen dioxide levels will be examined by the project group for the clean air plan.” The minutes of the latest meeting show a diesel vehicle ban in the Bonn environmental zone was seriously considered.

Besides an expansion of the environmental zone, the citizens’ action group Umweltschutz Bonn (Climate Protection Bonn), a member of the project group, is demanding additional drastic measures. These include a city toll and banning diesel vehicles, which emit more health damaging nitrogen dioxide than petrol engines, especially in the case of older vehicles. Chambers of industry and commerce and district worker associations have rejected a vehicle ban and are looking to incentives for more environmentally friendly forms of transport.

The district government has found the levels of pollutants in the air in Bonn are sinking, “but too slowly” according to Schneemann. One reason given for the levels not being met is the diesel car debacle in the car industry.

The NRW environmental ministry agrees. Their spokesperson, Tanja Albrecht, said a vehicle ban could not be ruled out, but: “We want to avoid this, so drivers do not pay for the car manufacturers’ illegal schemes.”

The city sees the reduction of car traffic and a strengthening of local public transport and cycling as its main goal. It is working on a mobility plan. The environmental office says there are no federal laws allowing a vehicle ban or a city toll. “The battle against pollution at its source, ie vehicle emissions, should be the priority before such drastic measures as vehicle bans are effected,” said Stefanie Zießnitz from the city press office.

(Original text: Philipp Königs. Translated by Kate Carey.)