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 4Â a.m., while all lines have services from about 5Â a.m. onwards. A full service is maintained from 6Â a.m. until about 8Â p.m., and a somewhat reduced service is run until the late evening. The last services leave Frankfurt at 2:12Â a.m. The S8/S9 runs 24/7.