The main aims of the M4 realization are:
- to realize a new diametrical line from East to West, in order to connect through the historical center some highly populated urban areas that are not well served by the network of public transport;
- to interconnect with the whole railway system, urban and regional;
- to realize a direct connection between the city center and Linate Airport.
The monitoring of the underpass has already ended. It allowed to control the geometry of the trails during the excavation done with 2 TBM, without interrupting or reducing the railway traffic. In case of an overcoming of the configured threshold, an alarm message reached the appointed people.
The monitoring of stations is divided into the monitoring of the bulkheads through load cells and inclinometer tubes, and the monitoring of the buildings with crackmeters, tiltmeters and H-Level. Manual and automatic readings allow to verify the design hypothesis.