The Grorud Line is a 13.0-kilometer long (8.1 mi) line on the Oslo Metro between Tøyen and Vestli in Oslo, Norway. Built as a mix of underground, at ground level and as an elevated line, it runs through the northern part of Groruddalen, serving such neighborhoods as Grorud, Romsås and Stovner. Line 5 runs along the entire line four times per hour. Line 4 runs between Vestli and Økern before branching off on the Løren Line to get onto the Ring Line. With 40,000 daily riders, the Grorud Line is the busiest branch of the metro.

MX3000 is an electric train used on Oslo Metro in Oslo, Norway. The multiple units are produced by Siemens Mobility, who started serial delivery in 2007. Seventy-eight three-car units were ordered by Sporveien, and five by Akershus County Municipality. They replaced the older T1000 and T1300 stock that was used on the Oslo Metro since 1966. By 2010, the last T1000 and T1300 trains had been retired and replaced by 83 three-car units. 32 additional sets were ordered, and the final train set was delivered in 2014, increasing the fleet to 115 units.