Copenhagen S-train Technical Overview

Copenhagen S-train Technical Overview

S-trains run on standard-gauge tracks and are powered via overhead wires. The voltage is 1,500 or 1,650 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. They 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.

From 1975 until 2022, the primary signalling system was a proprietary fixed-block cab signalling system called HKT that transmitted data to the trains via low-bandwidth audio frequency induction loops between the rails. Varying the combination of frequencies allowed up to 15 different instructions or commands – such as stops and permitted speeds – to be indicated to the train. Use of the permitted speed encoding provided full supervision of train speed, when a train running under HKT control entered a block with a lower target speed than the train's current speed it would initiate service braking until the two speeds matched. This, combined with the fact that all S-train stock had similar braking characteristics, allowed the assumption of reduced braking distances and the use of fixed blocks significantly shorter than on conventionally-signalled railways.

Lineside signals were provided for use when the HKT system was inoperative or when a non-equipped train needed to be driven on the line, but line capacity was significantly reduced as these signals only protected full-length blocks and had to be placed according to conservative braking distance assumptions.

In 2011, infrastructure operator Banedanmark awarded Siemens Mobility a contract to replace HKT with its Trainguard MT communications-based train control system (CBTC), on the grounds that the HTK installation was reaching the end of its life and becoming increasingly unreliable. The CBTC system employs the moving block principle, whereby a central controller continuously tracks the precise location and speed of every train on the line and adjusts the instructions issued to drivers accordingly. On the S-train network this has allowed a reduction in minimum separation between consecutive trains ('headway') from 120 seconds to only 90.

Hillerød–Jægersborg was the first section to be converted, as its F-HKT installation ('simplified' HKT) had the oldest hardware and did not deliver the same level of train protection as the other parts of the system. The new CBTC system entered service on this section on 29 February 2016. Further conversions continued through to 2022, when in late September the final three routes (Valby–Frederikssund, Valby–Høje Taastrup, and Sydhavn–Køge) were switched over to CBTC operation.

Copenhagen S-train Overview

Copenhagen S-train Locale: Copenhagen urban area
Copenhagen S-train Transit Type: Commuter rail
Copenhagen S-train Number of Lines: 7 with 7 services
Copenhagen S-train Number of Stations: 87
Copenhagen S-train Annual Ridership: 116 million (2016)
Copenhagen S-train Began Operation: 1934
Copenhagen S-train Operator(s): DSB S-tog
Copenhagen S-train System Length: 170 km
Copenhagen S-train Track Gauge: 1,435 mm (4 ft 8+1⁄2 in) standard gauge
Copenhagen S-train Electrification: 1,650 V DC overhead lines
Copenhagen S-train Top Speed: 120 km/h (75 mph)