This map shows Roslagsbanan, a narrow-gauge commuter railway that connects Stockholm with suburbs and countryside north-east of the city.
The terminal Stockholm Ö is not near the standard-gauge central station, but can be readched by the metro. A standard-gauge freight spur from Stockholm N passes under the line north of Stockholm Ö. Previously there has been a standard-gauge track leading down to Stockholm Ö for exchangning freight with Roslagsbanan, but only traces of it remains today, and the narrow-gauge line has no freight traffic.
The network is electified with 1.5 kV DC catenary; the signaling is mostly similar to the one Banverket uses for its standard-gauge railways. The trains are fairly modern 3-car DMUs, operated by Linjebuss (which, confusingly, people tell me is a Connex subsidiary - Connex operates the metro and the other railways owned by the Stockholm transit authority under its own name but calls itself Linjebuss at Roslagsbanan).