Project promoter Länsimetro Oy announced that the 14km rail track extension from Ruoholahti to Matinkylä in Helsinki will open on 15 August.

The newly laid track will also include eight stations.

Länsimetro stated that the project has an investment of €1.88bn, which is 28.3% more than initially planned. The seven-year project employed 1,500 people.

Excavation work began in November 2009 and tunneling works were completed in February 2014, while the laying of new tracks was completed in December 2015.

"Various systems will be tested at every station and trains will commence test runs in March."

Apart from new stations and two parallel tunnels, the project also involved building 15 vertical shafts for an emergency exit, ventilation, pressure relief and smoke extraction systems, as well as a total of 54 cross passages between the twin tunnels.

52 automation systems have been installed on the underground network for passenger safety.

Various systems will be tested at every station and trains will commence test runs in March.

Once these lines are opened to public, bus routes that earlier terminated in Kamppi will be extended to offer a linking service to Matinkylä and Tapiola under a plan by Helsinki Region Transport.

Underground trains currently operate at four-minute intervals during peak times, and these are expected to run more frequently in the future.

Two underground lines will be in operation, which are Matinkylä-Vuosaari and Tapiola-Mellunmäki. At peak times on weekdays, trains will run at 2.5-minute intervals on the section shared by both lines, which is Tapiola-Itäkeskus.

The firm also stated construction of the Matinkylä-Kivenlahti section is under way and will be completed in 2020.

Länsimetro Oy is a company jointly owned by the cities of Espoo and Helsinki. It has been entrusted with the task of constructing the West Metro underground line.