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| Milan Metro Line 4 | |
|---|---|
| Name | Line 4 |
| Type | Rapid transit |
| System | Milan Metro |
| Status | Operational |
| Locale | Milan, Lombardy |
| Start | San Cristoforo |
| End | Linate Airport |
| Stations | 21 (planned 22+) |
| Open | 26 November 2022 (initial section) |
| Owner | Azienda Trasporti Milanesi |
| Operator | Azienda Trasporti Milanesi |
| Character | Underground |
| Stock | Hitachi Rail Italy driverless trains |
| Linelength | 15.2 km (planned 17 km) |
| Electrification | 750 V DC third rail |
| Speed | 80 km/h (maximum) |
Milan Metro Line 4 is an automated rapid transit line serving Milan and providing a direct connection between southern districts and Linate Airport. Conceived as part of a package of network expansions including Line 5 and Line 3 upgrades, Line 4 emphasizes driverless operation, deep tunnelling, and high-frequency service. The project links key urban nodes such as Porta Romana, Duomo, and Corvetto with regional transport hubs including Milano Centrale railway station via interchange with existing lines.
Line 4 is a north-east–south-east axis designed to relieve congestion on Line 1 and to serve growing demand to Linate Airport and the Porta Vittoria corridor. Planned and executed under the auspices of Regione Lombardia, Comune di Milano, and Metropolitan City of Milan, the line received funding and oversight from institutions including European Investment Bank, Cassa Depositi e Prestiti, and private contractors led by WeBuild. The design prioritizes automation standards akin to those on Line 5 and technologies used in projects such as Copenhagen Metro and Vancouver SkyTrain.
The route traverses densely built urban fabric from San Cristoforo in the west to Linate Airport in the east, intersecting with major interchanges: Domodossola for Passante, Zara for Line 3 connections, and central nodes near Duomo for Line 1 transfer. Stations were sited to serve landmarks and institutions such as Policlinico, University of Milan precincts, and commercial hubs adjacent to Corso Buenos Aires. Architecture and wayfinding draw on precedents from Milan Cathedral area redevelopment and transit hubs like Gare du Nord and Saint-Lazare for passenger flows.
Construction employed tunnel boring machines similar to those used on the Gotthard Base Tunnel and complex diaphragm wall techniques analogous to work on Crossrail in London. Deep stations required precision engineering near heritage sites such as Castello Sforzesco and conservation protocols coordinated with Soprintendenza Archeologia, Belle Arti e Paesaggio. Civil contractors coordinated with firms experienced on projects like High Speed 2 and TAV corridors. Systems integration involved signalling suppliers familiar with Communications-based train control deployments used on Singapore MRT and Hong Kong MTR. Construction phases addressed utility relocations for ENEL networks and coordinated with A2A (company) for energy provision.
Line 4 operates driverless, fully automated trains supplied by Hitachi Rail Italy under CBTC supervision, reflecting automation standards seen on Paris Métro Line 14 and Barcelona Metro driverless lines. The fleet uses 750 V DC third rail electrification and platform screen doors for safety, similar to installations at Heathrow Airport and Incheon International Airport transit links. Operations, timetabling, and fare integration are managed by Azienda Trasporti Milanesi, coordinated with regional tickets such as those used by Trenord and intermodal connections to Malpensa Express services. Maintenance depots and control centres leverage best practices from Alstom and Siemens urban rail operations.
Projected ridership studies prepared with consultants experienced on RER (Île-de-France) and S-Bahn (Berlin) estimated significant modal shift from surface buses and private cars, with passenger flows concentrated at interchanges like Milano Centrale railway station and airport transfers to Linate Airport. The line aims to reduce road congestion near Corso Venezia and support economic activity in commercial corridors such as Porta Romana and Ripamonti. Environmental assessments referenced standards from European Commission transport policy and urban mobility plans developed with input from World Bank urban transport specialists.
Planned extensions consider further eastern and western links to municipalities in the Metropolitan City of Milan, with proposals engaging stakeholders such as Provincia di Monza e della Brianza and neighbouring communes including Segrate and Rozzano. Long-term interoperability studies explore integration with Pedemontana Lombarda regional schemes and potential connection to Malpensa Airport corridors. Funding and phasing remain subject to approvals by Ministero delle Infrastrutture e dei Trasporti and coordination with EU cohesion instruments.