The construction of the Western extension from Ruoholahti to Matinkylä in Espoo was approved by the Espoo city council in 2006.
Construction began in 2009 and the extension was opened in 18 November 2017.
This first stage of the extension was 14 km (8.7 mi) long, with eight new stations, two in Helsinki and six in Espoo and was built entirely in a tunnel excavated in bedrock.

After first stage of the Western extension opened the bus lines in Southern Espoo were reconfigured as feeder lines to either Matinkylä or Tapiola metro stations instead of terminating at Kamppi in the centre of Helsinki.

Before the extension of the metro, trains could be a maximum length of three units (each unit being two cars) but the new stations west of Ruoholahti were built shorter than the existing stations because it was originally planned to introduce driverless operation.
The driverless project was cancelled in 2015 but the shorter new stations mean that the maximum train length is reduced to two units which is actually shorter than before.
To increase capacity the automatic train protection system theoretically permits headway as short as 90 seconds, if needed in the future.
The construction of the Western extension from Ruoholahti to Matinkylä in Espoo was approved by the Espoo city council in 2006. Construction began in 2009 and the extension was opened in 18 November 2017. This first stage of the extension was 14 km (8.7 mi) long, with eight new stations, two in Helsinki and six in Espoo and was built entirely in a tunnel excavated in bedrock.
After first stage of the Western extension opened the bus lines in Southern Espoo were reconfigured as feeder lines to either Matinkylä or Tapiola metro stations instead of terminating at Kamppi in the centre of Helsinki.
Before the extension of the metro, trains could be a maximum length of three units (each unit being two cars) but the new stations west of Ruoholahti were built shorter than the existing stations because it was originally planned to introduce driverless operation. The driverless project was cancelled in 2015 but the shorter new stations mean that the maximum train length is reduced to two units which is actually shorter than before. To increase capacity the automatic train protection system theoretically permits headway as short as 90 seconds, if needed in the future.
Helsinki Metro