The initial motion for building a metropolitan railway system in Helsinki was made in September 1955, though during the five decades beforehand, the idea of a tunneled urban railway for Helsinki had surfaced several times.
A suburban traffic committee (Finnish: Esikaupunkiliikenteen suunnittelukomitea) was formed under the leadership of Reino Castrén, and in late 1955, the committee set to work on the issue of whether or not there was truly a need for a tunneled public transport system in Helsinki.
After nearly four years of work, the committee presented its findings to the city council.
The findings of the committee were clear: Helsinki needed a metro system built on separate right-of-way.
This was the first time the term "metro" was used to describe the planned system.
At the time the committee did not yet elaborate on what kind of vehicles should be used on the metro: trams, heavier rail vehicles, buses or trolleybuses were all alternatives.
The city council's reaction to the committee's presentation was largely apathetic, with several council members stating to the press that they did not understand anything about Castrén's presentation.

Despite the lacklustre reception, Castrén's committee was asked to continue its work, now as the metro committee, although very little funding was provided.
In spring 1963 the committee presented its proposal for the Helsinki Metro system.
On a technical level this proposal was very different from the system that was finally realised.
In the 1963 proposal the metro was planned as a light rail system, running in tunnels a maximum of 14 metres below the surface (compared to 30 metres in the finalized system), and with stations placed at shorter intervals (for instance, the committee's presentation shows ten stations between Sörnäinen and Ruoholahti, compared to the six in the realized system).
The Castrén Committee proposed for the system to be built in five phases, with the first complete by 1969 and the final by 2000, by which time the system would have a total length of 86.5 kilometres (53.7 mi) with 108 stations.
This was rejected after lengthy discussions as too extensive.
In 1964 the city commissioned experts from Hamburg, Stockholm and Copenhagen to evaluate the metro proposal.
Their opinions were unanimous: a metro was needed and the first sections should be built by 1970.

Although no official decision to build a system along the lines proposed by Castrén was ever made, several provisions for a light rail metro system were made during the 1950s–1960s, including separate lanes on the Kulosaari and Naurissaari bridges, and space for a metro station in the 1964 extension of Munkkivuori shopping center.
The RM 1, HM V and RM 3 trams built for the Helsinki tram system in the late 1950s were also equipped to be usable on the possible light rail metro lines.
The initial motion for building a metropolitan railway system in Helsinki was made in September 1955, though during the five decades beforehand, the idea of a tunneled urban railway for Helsinki had surfaced several times. A suburban traffic committee (Finnish: Esikaupunkiliikenteen suunnittelukomitea) was formed under the leadership of Reino Castrén, and in late 1955, the committee set to work on the issue of whether or not there was truly a need for a tunneled public transport system in Helsinki. After nearly four years of work, the committee presented its findings to the city council. The findings of the committee were clear: Helsinki needed a metro system built on separate right-of-way. This was the first time the term "metro" was used to describe the planned system. At the time the committee did not yet elaborate on what kind of vehicles should be used on the metro: trams, heavier rail vehicles, buses or trolleybuses were all alternatives. The city council's reaction to the committee's presentation was largely apathetic, with several council members stating to the press that they did not understand anything about Castrén's presentation.
Despite the lacklustre reception, Castrén's committee was asked to continue its work, now as the metro committee, although very little funding was provided. In spring 1963 the committee presented its proposal for the Helsinki Metro system. On a technical level this proposal was very different from the system that was finally realised. In the 1963 proposal the metro was planned as a light rail system, running in tunnels a maximum of 14 metres below the surface (compared to 30 metres in the finalized system), and with stations placed at shorter intervals (for instance, the committee's presentation shows ten stations between Sörnäinen and Ruoholahti, compared to the six in the realized system). The Castrén Committee proposed for the system to be built in five phases, with the first complete by 1969 and the final by 2000, by which time the system would have a total length of 86.5 kilometres (53.7 mi) with 108 stations. This was rejected after lengthy discussions as too extensive. In 1964 the city commissioned experts from Hamburg, Stockholm and Copenhagen to evaluate the metro proposal. Their opinions were unanimous: a metro was needed and the first sections should be built by 1970.
Although no official decision to build a system along the lines proposed by Castrén was ever made, several provisions for a light rail metro system were made during the 1950s–1960s, including separate lanes on the Kulosaari and Naurissaari bridges, and space for a metro station in the 1964 extension of Munkkivuori shopping center. The RM 1, HM V and RM 3 trams built for the Helsinki tram system in the late 1950s were also equipped to be usable on the possible light rail metro lines.
Helsinki Metro