It consists of four branches with terminals in Fruängen and Norsborg in the southwest and Mörby centrum and Ropsten in the northeast.

The 1965 Greater Stockholm Metro plan proposed to run the Red line further north, from Östermalmstorg to Hägernäs.

Stations were to be at Djursholms Ösby, Enebyberg, Roslags Näsby, Täby centrum, and Viggbyholm, terminating at Hägernäs.

The following year the County Council decided that a surface rapid transit line should be extended to Täby centrum.

In October 1980 the county council decided to continue with plans for the metro, but ultimately chose instead to in investments to the Roslagsbanan.

[4] For the other northern branch, which today ends in Ropsten, the proposal was to carry the metro on a separate rail-only bridge over Lilla Värtan and then in tunnel to a new station in Lidingö Centrum.

Nonertheless, the choice was made to invest in a new tram bridge, which will be cheaper and in general will provide similar travel times to Stockholm.

[4] The Red line is served by two routes—lines 13 and 14—and carried 507,850 passengers per working day (2019),[1] or approximately 128 million per year (2005).

Regular daytime service is a 5-minute headway on line 14 between Mörby center and Liljeholmen, and 10 minutes at other times.