Milan Metro blu line mm milano, represented by the blue color, crosses Milan in about 30 minutes, connecting San Cristoforo to Linate Airport. However, just days after the line's full opening in October 2024, the fully automated, driverless system—developed by Hitachi Rail—faced significant malfunctions that affected passenger service. This follows years of delays and setbacks, with construction starting in 2015 and multiple postponements due to financial and logistical issues.

The Milan Metro network, which has existed for 60 years (from November 1964 to November 2024), now includes five lines. Like Line 5 (M5), the new M4 is a fully automated, driverless metro. Trains are managed from the control room at ATM headquarters, and the integration with other lines ensures high frequency, increased efficiency, and enhanced safety, thanks to advanced technologies​