The service uses the tracks of the Main-Lahn Railway between Niedernhausen and Frankfurt Central Station. This route is also used by regional trains in the section Niedernhausen–Frankfurt-Höchst. Between Frankfurt-Höchst and Central Station this service shares the Main-Lahn line with freight and shunting operations. National and regional services use the parallel running Taunus railway in this section. The Main-Lahn railway was completed on 15 October 1877 and has been used by S-Bahn services since 1978.
The city tunnel is an underground, pure S-Bahn route used by almost all services (except for the S7 service which terminates at the central station). The tunnel was opened in four stages in 1978, 1983, 1990 and 1992. In a short section between Mühlberg and Offenbach-Kaiserlei the Frankfurt Schlachthof–Hanau railway is used. The section from Mühlberg to Offenbach Ost through the Offenbach City Tunnel was opened in 1995.
This line was opened on 1 December 1898 and has been used since 2003 only by S-Bahn services.
History
Year
Stations
Route
1974 (R2)
11
Niedernhausen – Frankfurt Hbf
1978
13 (+2)
Niedernhausen – Hauptwache
1983
14 (+1)
Niedernhausen – Konstablerwache
1990
17 (+3)
Niedernhausen – Frankfurt Süd
1992
16 (+1, -2)
Niedernhausen – Mühlberg
1995
17 (+2, -1)
Niedernhausen – Frankfurt Süd
2002
18 (+1)
Niedernhausen – Frankfurt Süd
2003
26 (+10, -2)
Niedernhausen – Dietzenbach
2007
27 (+1)
Niedernhausen – Dietzenbach
The S2 was one of the first six services of the Rhine-Main S-Bahn system. In a prior test operation it ran between Niedernhausen and Frankfurt Central Station. The service was then called R2 where the letter "R" stands for regional. In 1975 the R2 was the system's first service employing the class 420 trainset. After the opening of the Frankfurt Citytunnel the service was renamed to S2 and extended to the new Hauptwache underground station. Further extensions of the tunnel followed in 1983 (Konstablerwache) and 1990 (Ostendstraße and Lokalbahnhof) so that the Südbahnhof (South station) became the service's eastern terminal. After the opening of the eastern Citytunnel branch to the Mühlberg station in 1992 the S2 started operation in this section shutting down its service to Lokalbahnhof and Südbahnhof until in 1995 the service resumed its pre-1992 operation. In 2002, Eppstein-Bremthal station was completed increasing the number of stations to 18.
In 2003 the Offenbach Citytunnel and the Rodgau railway was included. After two years of construction work this route was changed to S-Bahn operation. Since then the new eastern terminal station is Dietzenbach. In 2007 the new Frankfurt-Zeilsheim station was included to the S2 service.
