The driverless light metro supplements the larger S-train rapid transit system, and is integrated with local DSB and regional (Øresundståg) trains and municipal Movia buses.

The M3 is a circle line connecting Copenhagen Central Station with Vesterbro, Frederiksberg, Nørrebro, Østerbro and Indre By districts.

[6] Platforms are – although shorter than originally planned – built to accommodate trains with four cars, and the automatic doors can be modified accordingly should the need arise.

[citation needed] The City Circle Line (Danish: Cityringen) is an entirely underground 15.5 km (9.6 mi) loop through central Copenhagen and Frederiksberg with 17 stops.

[10] The Sydhavn line will terminate at Copenhagen South Station where it will create a new regional rail transport hub by connecting the metro system to the S-train network, regional trains, and long-distance trains on the current lines and the high speed Copenhagen-Ringsted railway.

[13] Stage 2 involved the establishment of the company Frederiksbergbaneselskabet I/S in February 1995, owned 70% by the Ørestad Development Corporation and 30% by Frederiksberg Municipality.

The third stage would be built by Østamagerbaneselskabet I/S, established in September 1995 and owned 55% by the Ørestad Development Corporation and 45% by Copenhagen County.

[14] COMET was a single-purpose consortium composed of Astaldi, Bachy, SAE, Ilbau, NCC Rasmussen & Schiøtz Anlæg and Tarmac Construction.

From 1 January 2000, the S-train service from Solbjerg to Vanløse was terminated, and work commenced to rebuild the section to metro.

[25] The Herlev/Brønshøj line was ultimately dropped as the City of Copenhagen withdrew its share of the cost of the Nørrebro branch chamber in its 2009 budget, and the state refused to continue the project.

Any branch to the Herlev / Brønshøj region would now require a shutdown of the City Circle Line for an extended period of time.

[26][27] In March 2007, a proposal to establish a station at Valby, where the Carlsberg Group is planning an urban redevelopment, was scrapped.

The group argued that the line should have been built underground, citing concerns that it would create noise pollution and a physical barrier in Amager.

The jury noted the system's high regularity, safety and passenger satisfaction, as well as the efficient transport to the airport.

[33] Initially, the system operated trains from 01:00 to 05:00 only on Thursdays to Saturdays, but, starting on 19 March 2009, night service was extended to the rest of the week.

[37] Independent of the existing system, it circles the city centre and connects the areas of Østerbro, Nørrebro and Vesterbro to Frederiksberg and Indre By.

[38] On 7 January 2011 the new project called Cityringen started with the signing of new contracts by Metroselskabet, with Ansaldo Breda and Ansaldo Sts (Finmeccanica Group) for the supply of trains and control systems and with an Italian joint-venture led by Salin Construttori (about 60%) and Tecnimont (about 40%) with Seli as third partner for the construction part.

In July 2013, Natur- og Miljøklagenævnet, the environmental appeals board, ruled that the city was wrong to grant Metroselskabet permission for 24-hour work days and noise levels of up to 78 db at the Marmorkirken site.

This forced construction to stop work at 6PM until a final ruling was made, thus delaying the completion date.

[10] A northwestern expansion of the City Circle Line was planned, where M4 would have diverted at Nørrebro and run to the suburbs of Brønshøj and Gladsaxe.

In subsequent plans, the northern extension of the M4 was instead relocated as a Nordhavn branch which connects with the City Circle Line at Østerport.

The southern extension of the M4 will run from Copenhagen Central Station through Sydhavn to Ny Ellebjerg, where the M4 will link up with the S-train and regional train system.

The Danish Transport Authority (Trafikstyrelsen) has suggested converting the F-line of the S-train network to metro standard as an M5 line.

[51] In September 2011, the city of Copenhagen and neighbouring Malmö in Sweden announced that they were seeking European Union funding to study a potential metro line under the Øresund to the neighbourhood of Malmö Central Station, providing faster trips and additional capacity beyond that of the existing Øresund Bridge.

[52] The study, for which the EU granted funding in the following December,[53] will consider both a simple shuttle between the two stations and a continuous line integrated with the local transport networks on each side, and they anticipate a travel time of 15 minutes between the two city centers.

The system is divided into zones, and the fare structure is integrated with other public transport in Copenhagen, including the buses managed by Movia, local DSB trains and the S-train.

Holders of the Copenhagen Card museum pass ride free of charge, as do up to two children under twelve years of age accompanied by an adult.

[68] The contract to operate the system was made with Ansaldo STS, who has subcontracted it to Metro Service, a joint venture between them and Azienda Trasporti Milanesi (ATM), the public transport company of the city of Milan, Italy.

The ATP is responsible for keeping the trains' speed, ensuring that doors are closed before departure and switches are correctly set.

The safety and signaling specifications are based on the German BOStrab, and controlled by TÜV Rheinland and Det Norske Veritas under supervision of the Public Transport Authority.