As regular visitors to Germany we were surprised last week to find that taking the car into Cologne required an “Environmental Sticker”. This seems similar to the new laws in France in that taking your vehicle into towns requires this sticker to be shown. Took the risk for that trip but now have one on the car ready for next time. I have not found a list of towns but the stickers are not expensive or hard to get so it seems safer to just get one and not have to worry.
It is possible to get them from sources in Germany when visiting but they can also be ordered on line. Note that Googling brings up unofficial sites which “handle” your application and charge a large fee. Genuine on line applications are handled by TUV. Fill in a form, attach a copy of your V5 and pay via credit card. My sticker arrived in four days. It costs 6 Euros if you collect in person and (from memory) 15 Euros if you want it delivered to UK.
This is the link to the ordering site
http://www.tuev-sued.de/auto_fahrzeuge/feinstaub-plakette/feinstaubplakette_ausland/england
We haven’t bothered with the French one as we just arrive at Calais and turn left for Belgium !!