Map showing the Oslo Tramway in 1939. Colors show the lines by who built them, as all street lines were by then operated by Oslo Sporveier. The red lines show light rail, which were operated by various other companies, except the Kjelsås Line. 
Background (black and white) information is rendered based on OpenStreetMap, which as a CC-BY-SA-2.0 license. The various lines are traced by the uploader based on various maps of Oslo, who has also added the legend and place/line names. The map is created using Inkscape and Maperitive.
Own work
Alasdair McLellan