Helsinki light rail line 15

The "trunk bus line" 550, formerly branded Jokeri ("The Joker", after Joukkoliikenteen kehämäinen raideinvestointi – "A circular rail investment for public transportation"), has been converted to light rail. The city councils of Helsinki and Espoo approved the construction project in June 2016,[7][8] after the Finnish government decided to participate in funding the construction. The rail line was preliminarily projected to open in 2021.[9] The construction of the 25-kilometre (16 mi) light rail line, without rolling stock or a depot, was projected to cost 274 million euros as of June 2016, with rolling stock and a depot projected to additionally cost up to 95 and 65 million euros, respectively.[10]

The 550 was originally conceived as a light rail line in 1990, but only realised as a bus line in 2003. The general plans to convert the congested bus line to light rail were first published in 2009, but the decision to begin construction was only taken in June 2016 after many delays.[11][12][13][14] The municipality of Espoo has located the western terminus of the rail line at Keilaniemi instead of Tapiola. There are connections to the Metro at Aalto University and Keilaniemi.

The previous 550 bus line was a 25-kilometre-long (16 mi) orbital route running roughly parallel to the innermost ring road around Helsinki (Ring I). The 550 ran from Itäkeskus in the East to Tapiola in the West, connecting with the commuter rail network at Oulunkylä, Huopalahti, Pitäjänmäki and Leppävaara, and with the Metro in Itäkeskus and Tapiola.

Light rail line 15 is a significant development for the Helsinki tram network. The route is located entirely outside the current network, surrounding it; the length of the route constitutes a large proportion of the total network length, and the line is built to modern light rail standards (as opposed to the relatively old-fashioned street tram system). However, the new line is technically compatible with the existing network (1,000 mm (3 ft 3+3⁄8 in) metre gauge, low platforms). Direct integration with the Helsinki Metro (broad gauge, high platforms, planned driverless operation) was briefly studied in 2003, but it was found to be highly impractical.[15]

Construction on the line officially began in June 2019.[16] Construction proceeded ahead of schedule, with test runs being completed between 2022 and June 2023.[6] Regular service started in October 2023,[5] ahead of the original 2024 target date.[17] 5858 workers took part in the construction.[18]

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  Construction work in Maunula in September 2022
• 
  Western entrance of the Patterinmäki tunnel during construction work in May 2022