Sendlinger Tor, Odeonsplatz and Olympia-Einkaufszentrum also each have two quite separate stations at different levels, connected with each other by escalators and elevators. Frequency and scheduling Most lines operate with trains running at intervals of every 5 minutes during peak hours, but due to lines overlapping, a suitable train for a journey can be as frequent as every 2 minutes. Outside of peak times lines operate trains at frequencies of every 10 minutes; however, around the start of operations and after midnight the line frequency decreases to every 20 minutes or more on most lines. Again with line overlap this means that a suitable train will arrive (often much) more frequently. U1 In 1980 the U1 commenced operation together with the U8 (now U2). At the beginning it was only operating on a section of U2's track. When the branch to Rotkreuzplatz was opened, it became a separate line. The line's colour is green. Today the U1 has a length of and 15 stations. It starts at Olympia-Einkaufszentrum in the district of Moosach. The U3 was extended to the same station (but on a different level) in 2007. On the way south it follows Hanauer Straße to Georg-Brauchle-Ring, which has been designed by Franz Ackermann, reaching Westfriedhof. It continues via Gern to Rotkreuzplatz, which was its terminus from 1983 to 1998. Below Nymphenburger Straße it goes on to Maillingerstraße and Stiglmaierplatz and finally merges into the U2 track at München Hauptbahnhof. On the busy city section, U1 and U2 run with a 5-minute offset, yielding 5 minute intervals even beyond peak hours. At Central Station, it also crosses the S-Bahn and U4/U5. At the next station, Sendlinger Tor, it passes below U3/U6. There the U1/U2 platforms for each direction lie in tunnels which are apart from each other and are connected by a pedestrian tunnel. Fraunhoferstraße, the next station, is also reached in separate tunnels, which had to be excavated using tunneling shields due to the proximity of the River Isar. However, the two tubes are connected by the platform, which demanded large pillars that are characteristic for this station. The next station, Kolumbusplatz, is a junction which has three tracks. Here the U1 branches off the U2 again. The southbound branch line was opened in 1997 and traverses the colourful station Candidplatz, eventually reaching Wettersteinplatz. The following station, St.-Quirin-Platz has an extraordinary architecture, as it is covered by a