LEZs in the following countries require action before you enter the zone:
In Austria; in windscreen stickers are increasingly needed in the Austrian LEZs. Stickers are required for Vienna and Niederösterreich, and are likely to be required in other Austrian LEZs soon. In LEZs where a sticker is not yet required, you need to show your vehicle papers in a traffic check.
In Germany a windscreen sticker is required for German LEZs. Stickers [plakette in German] can be bought from garages, testing stations [TÜV], the LEZ city administration, or online, for example from TÜV-Nord in several languages.
In the Netherlands, Dutch vehicles are registered through the national database and foreign vehicles are not enforced.
In Sweden you need get a sticker for the windscreen.
In Prague you need a windscreen sticker (either a Czech or German one) once the LEZ starts.
For the Mont Blanc Tunnel, the price depends on the Euro standard. This is controlled manually at the toll point, Euro standard is estimated by the age of the vehicle.
In Norway once the LEZs are in operation, you will need to ensure that you pay the tolls if your vehicle is less than Euro 4. This is likely to use the same system as is used for the urban road tolling, see for example the Oslo charging scheme, or www.autopass.no/visitors.