The system is complemented by the Copenhagen Metro and an extensive bus network. Although owned by different companies, all three systems use interchangeable tickets. Most of the city's bus terminals are located adjacent to an S-train station.
In the city center, the trains run below ground level with one underground station. Outside the inner city it runs in the open, often on embankments. Although the S-trains run parallel to the regional/intercity mainline tracks between Høje Taastrup and Klampenborg, they have their own separate trackage all the way with different signalling and power standards from the mainline tracks. A handful of track connections between S-train and mainline tracks exist but are used only in special circumstances (mostly by maintenance vehicles).
The northern radials are
The six radials are additionally connected by
See articles about each of the seven components for station lists and service patterns.
Some services (E, H and Bx) skip certain stops to provide faster travel time, but no trains skip stops inside the ring line.
|Name||Southern end||Runs when||Northern end|
|all stops to Hundige||Køgebugtbanen||All week, all day||Hareskovbanen||all stops to Farum|
|all stops to Høje Taastrup||Vestbanen||All week, all day||Nordbanen||all stops to Holte|
|limited stops to Høje Taastrup||Vestbanen||Mo-Fr, rush hour||Hareskovbanen||limited stops to Farum|
| all stops to Ballerup,|
every second train continues to Frederikssund
|Frederikssundbanen||Mo-Sa, daytime||Klampenborgbanen||all stops to Klampenborg|
|all stops to Ballerup||All other times|
|limited stops to Hundige, then all stops to Køge||Køgebugtbanen||All week, all day||Nordbanen||limited stops to Holte, then all stops to Hillerød|
|all stops to Ny Ellebjerg||Ringbanen||All week, all day||Ringbanen||all stops to Hellerup|
|limited stops to Frederikssund||Frederikssundbanen||All week, all day||(terminates at Østerport)|
Before 2007, the timetable followed a principle that each named line would run on a strict 20-minute schedule. In periods where more than 3 trains an hour were needed, the extra trains would be given separate service designations; for example there was a service B+ which ran on the same route as B, but only in the daytime and with its departure times offset 10 minutes from B.
Earlier timetables also had express services that skipped stops inside the ring line.
The S-trains run on standard gauge railway tracks and are powered by overhead wires. The voltage is variously quoted as 1500 or 1650 volts DC (negative overhead wire), indicating that it varies considerably with the loading and distance from a feeder station. Power is drawn from the national grid through 38 feeder stations spread around the network. The feeder stations have to be relatively close to each other because the large currents in the overhead wires (caused by the relatively low voltage) would lead to unacceptably large transmission losses otherwise.
The primary signalling system is a fixed-block cab signalling system called HKT which transmits data to the trains through low-bandwidth audio frequency induction loops between the rails. Different frequency combinations encode different target speeds; when a train enters a block with a lower target speed than its current speed it will initiate a service braking until the two match. This allows blocks to be much shorter than the full-speed braking distance, but as the braking profile is encoded in the transmitted target speed it only works where all trains have similar braking characteristics.
Lineside light signals are also provided for use in case of HKT failures or the occasional visit of a non-S-train, but the lineside blocks are longer, so capacity in this mode is reduced. Together with the finished ring-line, the exact train positions are now visible on all lines in Byens puls (see links below).
The trains are 8-car articulated units (DSB class SA-SD) supplied by Linke-Hofmann-Busch/Siemens. The cars are shorter than conventional railway cars; each has a single axle under one end of the car; the other end is supported by the neighbouring car. (The end cars are exceptions and have two axles each). The units have automatic Scharfenberg couplers at the ends; in peak hours most trains consist of two coupled units, giving a total train length of 168 meters. There are also a small number of 4-car units (class SE-SH) that can run solo in low-traffic intervals. The top speed is .
Trains of an older and more conventional design (DSB class MM-FU-MU-FS, built 1967-1978, and FC-MC-MC-FC, built 1985-1986) ran until January 7, 2007. All MM units have been retired and scrapped except for a few set aside for museum use; the MC units are currently being scrapped at Holbæk harbour. An official ceremony was held February 3, 2007 with the last ride of the 2nd generation S-trains. One of the spared museum trains will hopefully be prepared by DJK (Danish Railroad Club), who now are the owners of the train, and will eventually make its way to the tracks again on special occasions such as anniversaries.
In February-March 1934, the newspaper Politiken asked its readers to coin a name for the new system of commuter trains. "S-train" was the winning proposal, made independently by several readers. The judges' panel (headed by the director-general of the DSB) cited a long list possible expansions in their motivation, including choices such as "state railways", "city railway", "Greater Copenhagen", "sun", "lake", "forest", "beach", "snow", "skiing", "skating", "sleigh", all of which start with an S in Danish. (It shows that the initial marketing of the S-trains emphasized recreational day trips from the city to the countryside).