Deutsche Umwelthilfe (DUH), an environmental NGO, is suing Mainz, arguing that the city exceeded legally-acceptable levels of pollution last year. The nitrogen dioxide (NO2) emissions averaged 48 micrograms per cubic meter of air in 2017, while the Europe-wide limit is 40 micrograms, according to the Federal Environmental Agency.
The air on a busy thoroughfare near the city's main train station has been cited as particularly polluted. The city argues that pollution levels will be offset in 2019 through the expansion of the tram network and the introduction of a new bus fleet.
The DUH is calling for a blanket ban in the area on diesel cars, suggesting that it is the only way that air pollution will be reduced.
Fuel for thought
In other large German cities where air quality is bad, the limit for nitrogen dioxide emissions is often exceeded. The substance can cause respiratory issues or lead to cardiovascular diseases – exhaust fumes from diesel vehicles are one of the main contributors to the phenomenon.
In February, the Federal Administrative Court in Leipzig ruled that driving bans are generally admissible – but they must be proportionate.
As a result, Hamburg has banned diesel cars from two sections of road. In Stuttgart, a large-scale entry ban for older diesel vehicles is planned in 2019. Frankfurt am Main is exploring a ban for diesel cars in the commuter metropolis, while Berlin is set to follow suit.
READ ALSO: Court orders diesel ban on some Berlin streets
A renewed focus on air quality in the wake of Volkswagen's 2015 "dieselgate" scandal - in which the car giant admitted to cheating regulatory tests on 11 million cars worldwide - has seen a wave of courtroom action across Germany.
And there's more to come. The Administrative Court of Cologne is expected to rule on a driving ban for diesel vehicles in the cities of Cologne and Bonn on November 8th.
The bans in different German cities have tended to restrict the use of diesel cars in specific zones, such as the city centre.
Diesel or no diesel?
Critics say the driving ban will affect vehicle owners with an existing euro norm 4 or 5 environmental clearance for diesel-powered vehicles.
The ban will prevent commuters from reaching work and will simply intensify congestion on alternative roads. Those against the ban argue that controls will also not be easy to implement. Advocates, on the other hand, argue that driving bans are the only effective way to reduce emissions as fast as possible, thereby making the air cleaner.
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