Since the beginning of 2008, the inner city within the S-Bahn ring has been a designated ‘Green Zone’ (Umweltzone), meaning all cars must carry a green, yellow or red sticker - depending on their emissions class. From January 1, 2009 all cars with yellow and red stickers will be banned from the Green Zone. Travelers driving into central Berlin (and Hanover, Cologne and Stuttgart) can find more information and purchase stickers here: http://car-germany.eu
