The catalytic converters for diesel cars were supposed to upgrade older vehicles to Euro standard 6. Even before the development, experts warned that the retrofitting would be technically too complex and expensive, and would not be worthwhile. Environmental organisations and the party "die Grünen" nevertheless insisted on the technology.
With the help of a technical retrofit, Euro 5 diesel vehicles were to be upgraded to Euro 6. The SCR catalytic converters, which have been mandatory since the latest Euro standard, should thus also be retrofitted in Euro 5 vehicles. Especially in view of the diesel driving bans announced in many places in Germany, this was seen as an opportunity to reduce the vehicles' nitrogen oxide emissions and thus to allow them to continue to enter the threatening diesel driving ban zones.
Many of these diesel driving bans are now off the table. But already at the beginning of the discussion about hardware retrofitting for diesel cars, when diesel driving bans were imminent in many places, car manufacturers warned that the technology was too complex and expensive. In order to be able to guarantee the functionality of the catalytic converters, large development teams would have to supervise the projects for years. Instead, the experts wanted to use software updates, which were ordered by the authorities for many models anyway, for example because of the diesel scandal. The independent science academy Leopoldina also criticised that the hardware solution was too costly and also led to increased CO2 emissions from the vehicles.
Due to pressure from various organisations such as the German Environmental Aid (DUH) and the ADAC, but also from the party "die Grünen", the catalytic converters were developed anyway. The automobile industry had to invest millions to make the installation of the catalytic converters possible. In addition, they gave customers subsidies of up to €3,000.
The opponents of retrofitting were probably right. The demand for the technology is vanishingly small. So far, Daimler has installed just 900 SCR catalytic converters, VW only 195, even though millions of Euro 5 diesel vehicles are on the roads in Germany. Despite the experts' predictions, the low demand is astounding. In many places, citizens complained that Euro 5 vehicles would fall victim to potential driving bans, but they do not use the technology developed especially for this purpose.
The development of diesel driving bans was probably not correctly predicted by politicians. For them, it should be an indicator that technology that is promising on paper does not always work in reality. However, it remains difficult to blindly trust the experts in the automotive industry when cheating, as in the case of the diesel scandal, causes trust in the automotive industry to disappear.
You can see where there are diesel driving ban zones in Germany in our Green-Zones app.