The City Circle Line () or M3 is a loop line of the Copenhagen Metro. It has been claimed by COWI A/S that the City Circle Line is the largest construction project to have taken place in Copenhagen during the last 400 years. The network's total length is and has 17 stations. The line opened on 29 September 2019. Plans for its construction were approved by the Danish Parliament on 1 June 2007. Preferred bidders were announced during November 2010. The total cost was estimated at 15 billion kroner but had risen to 21.3 billion kroner ($ billion) when the contractors were announced in late 2010. It is a fully automated line, using driverless trains and capable of routine 24/7 operations. Italian rolling stock manufacturer AnsaldoBreda provides the trains for the new line, and the stations are intentionally similar to the Copenhagen Metro's existing stations. The transit agency Movia has projected that up to 34 million passengers eventually switch from buses to using the Metro during each year. History Background During 2002, the Copenhagen Metro, a fully automated driverless metro system, was opened. It quickly became known for its high level of reliability, attaining an operational punctuality in excess of 98 per cent of on-time arrivals. Due to its success, during 2005, plans were put forward for further expansion of Copenhagen Metro in the form of the City Circle Line. As proposed, it involved the construction of a underground circular route, a total of 17 stations, and emergency escape shafts, to support two new underground lines, designated as M3 and M4. The planned City Circle Line would connect into the Kongens Nytorv and Frederiksberg stations of the preexisting metro network. During the summer of 2007, the Danish Parliament gave its approval for the construction of the proposed line, although it would be another four years before construction activity would commence. At the time of its approval, the project had an projected cost of DKK21.3 billion ($3.2 billion) along with an anticipated date of completion by July 2019. Transport group Metroselskabet held overall responsibility for the City Circle Line. Contracting On 7 January 2011, the civil engineering contract for the City Circle Line was awarded to the Copenhagen Metro Team (CMT), a joint venture comprising Salini Impregilo, Technimont, and SELI. Italian rail equipment specialist Hitachi Rail STS was selected to supply the trains, electrical infrastructure and communications systems, supervisory control and