Aachen could become the second German city to introduce a ban on diesel vehicles, following legal action brought by two environmental groups, the final hearing for which is on Friday.

Aachen looks likely to face a diesel ban following Friday’s hearing.

The case dates back to November 2015, with Deutsche Unwelthilfe (DUH) and ClientEarth bringing legal action for the city’s air pollution breaching EU limits, but the hearing had been delayed until the Federal Administrative Court, Germany’s highest court, had ruled on local air quality zones in February.

As a result, it means local courts can ban the most polluting diesel vehicles from city centres; Hamburg did so in May, and Aachen is expected to follow suit later this week.

ClientEarth lawyer Ugo Taddei said the ruling in Liepzig marked a turning point: “Beyond local bans, we need a coherent and ambitious framework from the government, aimed at delivering genuine NO2 reductions in all polluted areas to protect people’s health. Without it, we may end up with clashing measures in different parts of Germany. That’s bad for motorists and shows a real failure by the government.”