By rosebell
On October 12, 2024, Milan celebrated the inauguration of the final section of its Line 4, also known as the Blue Line, connecting San Babila to San Cristoforo. This stretch, which adds 13 new stations to the network, was unveiled in a ceremony attended by Italy’s Minister of Infrastructure and Transport, Matteo Salvini, Milan’s Mayor Beppe Sala, and Webuild CEO Pietro Salini. The first segment of the Blue Line, running from San Babila to Linate Airport, has been operational since July 2023.
The development of the Blue Line involved a massive workforce of 17,000 people and the collaboration of 1,800 companies. The construction was managed by MM Spa, with M4 Spa, a consortium of major stakeholders including Webuild Italia SpA, the Municipality of Milan, ATM Spa, Hitachi Rail STS SpA, Mer Mec STE Srl, and Sirti SpA, playing a central role.
At a depth of up to 30 meters, the Blue Line is the deepest metro line in Milan. Its construction required the excavation of 25 km of tunnels, with some stations built just 1.5 meters from the foundations of nearby buildings. The project also employed innovative techniques, such as the freezing method using liquid nitrogen to stabilize groundwater during the construction of secondary tunnels. Approximately 1.5 million cubic meters of earth were removed during the process.
The Blue Line now spans 15 km with 21 stations, linking the city from east to west, from San Cristoforo to Linate Airport. Capable of handling 24,000 passengers per hour in each direction, the line is expected to serve 86 million passengers annually. Fully automated and driverless, the M4 ensures maximum safety for its riders, marking a significant advancement in Milan’s public transportation system.
