M4 (Milan Metro)

M4 (Milan Metro)
Name	M4
Type	Rapid transit
System	Milan Metro
Status	Operational
Locale	Milan, Lombardy, Italy
Start	Linate Airport
End	San Cristoforo railway station
Stations	21
Opened	2022 (initial section)
Owner	Comune di Milano
Operator	Azienda Trasporti Milanesi
Stock	AnsaldoBreda Driverless trains
Linelength	15.2 km
Electrification	750 V DC third rail

M4 (Milan Metro) is the fourth rapid transit line of the Milan Metro network serving Milan in Lombardy, Italy. It links Linate Airport with the southwestern districts of San Cristoforo and central hubs such as Piazza Duomo and Porta Venezia, providing automated, driverless service and modern infrastructure. The line is notable for its tunnelling under historic fabric, integration with regional rail nodes like Milano Centrale railway station, and connections to the urban tram network operated by Azienda Trasporti Milanesi.

Overview

M4 connects major transport nodes including Linate Airport, Piazza Duomo, Porta Garibaldi railway station, and San Cristoforo railway station across Milan and adjacent municipalities such as San Donato Milanese. Funded through partnerships involving the Comune di Milano, Regione Lombardia, and national bodies including the Ministry of Infrastructure and Transport (Italy), the line forms part of broader mobility policies alongside projects like M5 (Milan Metro), Passante railway (Milan), and the high-speed network linking Milano Centrale railway station with Torino Porta Nuova railway station.

Route and stations

The M4 alignment runs from Linate Airport in the east to San Cristoforo railway station in the southwest, serving 21 stations including interchanges with M2 (Milan Metro) at Centrale FS, M1 (Milan Metro) at Duomo, and M5 (Milan Metro) at Porta Garibaldi. Key stations include San Babila, Missori, and Sant'Ambrogio, providing access to landmarks such as Castello Sforzesco, Teatro alla Scala, and Basilica di Sant'Ambrogio. The route intersects with regional and suburban lines like Line S1 (Milan suburban railway service), Line S5 (Milan suburban railway service), and integrated services at Milano Centrale railway station.

History and development

Conceived during urban mobility plans influenced by events like Expo 2015 and policy frameworks from Regione Lombardia, the M4 project evolved from feasibility studies commissioned by the Comune di Milano and executed by consortia including firms such as AnsaldoBreda and Salini Impregilo. Initial proposals sought to relieve surface congestion on arteries like Viale Monza and improve access to Linate Airport following earlier proposals for an airport rail link. Construction phases coincided with large infrastructure programs overseen by national entities including the Ministero delle Infrastrutture e dei Trasporti and negotiations with heritage bodies such as the Soprintendenza Archeologia, Belle Arti e Paesaggio per la Città metropolitana di Milano.

Rolling stock and technology

Rolling stock comprises fully automated, driverless trains designed and supplied by industrial groups including AnsaldoBreda and subcontractors linked to the Hitachi Rail family. Trains operate on 750 V DC third-rail electrification and employ platform screen doors at stations for safety, similar to deployments on M5 (Milan Metro) and other automated metros like Copenhagen Metro and Dubai Metro. Control and signalling use CBTC-derived systems compatible with operations in networks engineered by companies such as Alstom and Siemens Mobility. Stations feature accessibility measures complying with standards promoted by the European Union and Italian accessibility regulations.

Operations and service patterns

Services are operated by Azienda Trasporti Milanesi with timetable integration into the urban fare system coordinated with entities like ATM Milano Card and regional travel authorities including Regione Lombardia. Typical frequencies reach high peak intervals, offering rapid airport transit comparable to links such as the Heathrow Express and urban metros serving airports like Schiphol and Barajas. Interchange at Centrale FS facilitates connections to long-distance operators including Trenitalia and Italo, while integration with surface trams and buses links to routes operated by ATM Milano and regional carriers.

Construction and engineering

Construction used tunnel boring machines (TBMs) in dense urban fabric beneath historic districts such as Centro Storico di Milano and required archaeological monitoring coordinated with the Soprintendenza. Engineering solutions addressed groundwater management near the Navigli canals and structural protection for monuments like Duomo di Milano and Santa Maria delle Grazie, site of The Last Supper by Leonardo da Vinci. Major contractors included multinational consortia with firms like Webuild (formerly Salini Impregilo), employing methods tested on projects such as the Gotthard Base Tunnel and cross-city tunnelling programmes in Paris and London.

Impact and future extensions

M4 has reshaped urban mobility in Milan, easing pressure on roads such as Corso Buenos Aires and enhancing access to commercial areas including Corso Vittorio Emanuele II. Economic impacts mirror studies from urban projects like the Porta Nuova regeneration and transport-led regeneration seen in Genoa and Turin. Planned extensions and studies consider connecting further suburban municipalities and improving multimodal hubs with Malpensa Airport links and regional rail enhancements coordinated by Rete Ferroviaria Italiana and City of Milan planning departments. Discussions involve EU funding instruments and frameworks such as the European Regional Development Fund to support future phases.

Category:Rail transport in Milan Category:Milan Metro lines