S1 (Rhine-Main S-Bahn)

S1
S1 in Hochheim, bound for Wiesbaden
Overview
Type	Rapid transit, Commuter rail
System	S-Bahn Rhein-Main
Status	Operational
Locale	Frankfurt Rhine-Main
Termini	Wiesbaden Hauptbahnhof Rödermark-Ober-Roden
Stations	32
Services	Taunus Railway, Main-Lahn Railway, Citytunnel Frankfurt, Rodgau Railway
Line number	1
Operation
Opened	28 May 1978 (1978-05-28)
Owner	Rhein-Main-Verkehrsverbund
Operator(s)	DB Regio
Depot(s)	Frankfurt Hbf
Rolling stock	DBAG Class 430
Technical
Line length	72.1 km (44.8 mi)
Track gauge	1,435 mm (4 ft 8 1⁄2 in) standard gauge
Electrification	Overhead line
Route number	645.1

The S1 service of the S-Bahn Rhein-Main system bearing the KBS (German scheduled railway route) number 645.1 is an important railway connection running east-west. It operates between the Hesse state capital Wiesbaden and the southern Offenbach rural district serving the densely populated area along the Main river.

With a route length of over 70 km (43 mi), 30 stations and a journey time of 87 minutes, it is the longest S-Bahn service in the Rhine-Main area. The average speed of travel is about 49.72 km/h (30.9 mph) and a station distance of about 2 km (1.2 mi).

Usually DBAG Class 423 railcars are used on this service. Its predecessor class 420 is only used for shortened shuttle services.

The western branch of the service starts at the central station of Wiesbaden and utilises the oldest railway route of the Rhine-Main area running between Mainz-Kastel and Frankfurt-Höchst parallel to the Main and the Taunus mountains from which the railway line derived its name. The about 31 km (19 mi) long route crosses the southern part of Wiesbaden, the Main-Taunus-Kreis and the westernmost part of Frankfurt. The service uses the existing double track route together with national, regional, and freight transportation. It serves eight stations. The Taunus Railway was opened in stages between 26 September 1839 and 19 May 1840 and has been used by S-Bahn services since 1978.

Between Farbwerke and Frankfurt-Griesheim 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 South Main railway is used. The section from Mühlberg to Offenbach Ost through the Offenbach City Tunnel was opened in 1995.