The German government is about to clear the way for the country’s local cities to legally drive older diesel cars off the road. And it’s not the first time German cities have moved to put the squeeze on older vehicles.

At the beginning of 2008, a number of German cities and towns started to institute what were called low-emission ‘Umwelt’ Zones. To access these areas, your vehicle needed to have an engine with a Euro 4 pollution rating.

Euro 4 cars got a green sticker for the windscreen, Euro 3 and Euro 2 cars got a yellow and red sticker, respectively.

According to the website dedicated to ‘Environmental’ Zones, the latest was brought in on the 1 April this year at Marburg, bringing the number up to 53, with 51 of them demanding a green sticker.

However, after ‘dieselgate’ became global news last year, governments and campaigners have had to admit that obsessing over CO2 emissions - a harmless gas locally, and one much appreciated by trees - had led European cities into the far more serious problem of the toxic pollution emitted by ‘low CO2’ diesel engines.

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Diesel sales account for around half of the overall UK and EU new car markets. For commercial vehicles - of the type that might spend all day on the roads - the diesel share is virtually 100 percent.

It’s no wonder that many German authorities have baulked at banning any vehicle that didn’t have a Euro 6 pollution rating. After all, there are many drivers out there, in relatively modern Euro 5 vehicles, who would suddenly find themselves banned from 51 city centres.

But, as the old political cliché goes, no government should let a good crisis go to waste. By putting the arm on older diesel engines, it might be able to push many drivers into showrooms to buy a brand new car, as well as giving a much-needed boost to the petrol-hybrid cars being sold - in very small numbers - by the German car industry.

Still, this doesn’t solve the diesel problem. According to the Euro 6 regulations, NOx exhaust emissions should not rise above 80 milligrams per kilometre. With real-world pollution testing now on the horizon - replacing the hopelessly lax lab-testing regime - diesel engines are set to be embarrassed again.