The Rhine-Main S-Bahn system is an integrated rapid transit and commuter train system for the Frankfurt/Rhine-Main region, which includes the cities Frankfurt am Main, Wiesbaden, Mainz, Offenbach am Main, Hanau and Darmstadt. The network comprises nine S-Bahn lines, eight of which currently travel through the cornerstone of the system, a tunnel (the "City Tunnel") through central Frankfurt. The first section of this tunnel was opened on May 28, 1978. Further tunnel sections were opened in 1983 and 1990, before its completion in 1992. The system belongs to the Rhein-Main-Verkehrsverbund (RMV) and is operated by DB Regio, a subsidiary of Deutsche Bahn. End-to-end journey times on the nine lines in the system range from 36 minutes (on line S7) up to 87 minutes (on line S1). The longest journey time into central Frankfurt (Hauptwache), from any point on the network, is 54 minutes. Services on some lines start shortly after 4a.m., while all lines have services from about 5a.m. onwards. A full service is maintained from 6a.m. until about 8p.m., and a somewhat reduced service is run until the late evening. The last services leave Frankfurt at about 1:20 a.m. The S8/S9 runs 24/7. The S-Bahn system is quite closely integrated with other components of the region's transport system, such as the bus services in the various cities and towns, the tram services in Mainz, Frankfurt and Darmstadt, and the Frankfurt U-Bahn. In Frankfurt, connections can be made, at either Hauptwache or its neighbouring station Konstablerwache, between the eight cross-city S-Bahn lines and eight of the city's nine U-Bahn lines, while the S-Bahn stations Frankfurt Hauptbahnhof and Frankfurt Süd between them have connection to six of the U-Bahn lines and any of the city's tram lines. Some opportunities for interchange also exist in the suburbs of Frankfurt. Lines Since the end of 2003, the system comprises the following lines: The former routes are as follows: Network map History The Early Years Plans for a rail connection between the central rail station (Hauptbahnhof) in Frankfurt and the Hauptwache, the central commuter destination in the city, were started in the early 1960s. Construction work on the project started in 1969. During the construction phase, some rearrangements were carried out to the commuter network in the area around Frankfurt, including creation of a link line between Bad Soden am Taunus and Niederhöchstadt. In 1978 the first section of the "Citytunnel" of the Rhine-Main S-Bahn