Signalling of the Milan Metro

An FS like signal in Crescenzago station

Line 2 uses a speed signaling system. Trains are directed using a semaphore system, which has five states:

• Imperative red: The train must stop.
• Permissive red: The train can go on with a maximum speed of 15 km/h (9 mph) and must stop in case of danger. Physically, it's represented by a fixed or flashing "P" under the semaphore.
• Red-yellow: The train can reach 30 km/h (18 mph).
• Yellow: The train can reach 50 km/h (31 mph).
• Green: The train can reach the line's speed limit: 85 km/h (53 mph) for the red line and 75 km/h (47 mph) for the green line.

Before 2011, Line 1 used this same system, but now uses a new signaling apparatus. The signaling apparatus permits a 90-second frequency on the line, similar to the one used on the M3 line. The speed of the train is decided by an ATC system and a two-color semaphore system. [2]

The two-color semaphore system has three possible states:

• Red: Imperative red.
• Red and white: Conditional green.
• White: Green.

Line 3 has an ATO/ATP system, so the driver must only check the doors and give consent to the electronic system to start the train.[3]

Line 5 uses AnsaldoBreda Driverless Metro, consequently the line does not have classical light signaling. Automatic signaling permits a frequency of a train every 75 seconds, but today only a 90-second frequency is used.[4]

• Italian railway signalling