[2] The proposal for a third metro line was approved by the municipal government of Milan in 1977.

[3] The first section, from Centrale to Duomo opened on 3 May 1990, just in time for the beginning of the World Cup.

[4] New extensions to Sondrio to the north and to San Donato to the south opened on 12 May 1991.

[6] The line, 16.6-kilometre long with 21 stations, runs from Comasina to San Donato, entirely underground Trains use an overhead contact system providing a voltage of 1,500 V DC.

[7] Although the project was approved in 2010, it was put on hold in early 2011 due to lack of funds.