and specialist printing, with renowned houses such as Georg von Holtzbrinck Publishing Group, Ernst Klett Verlag (schoolbooks), Kohlhammer Verlag, Metzler Verlag and Motor Presse having their head offices there. The Reclam Verlag is located in nearby Ditzingen. The newspapers Stuttgarter Zeitung (StZ; regional, with significant supra-regional, national and international sections) and Stuttgarter Nachrichten (StN; regional) are published here as well as a number of smaller, local papers such as Cannstatter Zeitung. As is the case wherever the US military is stationed, there is an American Forces Network (AFN) station. It transmits on FM on 102.3 MHz from Fernmeldeturm Frauenkopf and on AM on 1143 kHz from Hirschlanden transmitter. Transport Following the suit of other German cities such as Berlin, Cologne and Hanover, on 1 March 2008 a low emission zone (LEZ) came into effect in Stuttgart with the aim of improving air quality. This affects all vehicles entering the Stuttgart 'Environmental zone' (Umweltzone), including vehicles from abroad. Local transport Stuttgart has a light rail system known as the Stuttgart Stadtbahn. In the city center and densely built-up areas, the Stadtbahn runs underground. Stations are signposted with a 'U' symbol, which stands for Untergrundbahn (underground rail). Until 2007, Stuttgart also operated regular trams. Stuttgart also has a large bus network. Stadtbahn lines and buses are operated by the Stuttgarter Straßenbahnen AG (SSB). The outlying suburbs of Stuttgart and nearby towns are served by a suburban railway system called the Stuttgart S-Bahn, using tracks supplied by the national Deutsche Bahn AG (DB). A peculiarity of Stuttgart is the Zahnradbahn, a rack railway that is powered by electricity and operates between Marienplatz in the southern inner-city district of the city and the district of Degerloch. It is the only urban rack railway in Germany. Stuttgart also has a Standseilbahn, a funicular railway that operates in the Heslach area and the forest cemetery (Waldfriedhof). In Killesberg Park, on a prominent hill overlooking the city, there is the miniature railway run by diesel (and on weekends with steam). Rail links Stuttgart is a hub in the Intercity-Express and Intercity networks of Deutsche Bahn AG (DB), with through services to most other major German cities. It also operates international services to Strasbourg, Vienna, Zürich and Paris (five times a day, journey time 3 hours 11 minutes). Long-distance trains stop at Stuttgart Hauptbahnhof, the city's main line terminus, which is also used by Interregio-Express, Regional-Express and Regionalbahn