Metropolitan railways are urban, electric transport systems with high capacity and a high frequency of service.
Metros are totally independent from other traffic, road or pedestrians. They are consequently designed in tunnel, viaducts or on surface level but with physical separation. Metropolitan railways are the optimal public transport mode for a high capacity line or network service.
Some systems run on rubber-tyres but are based on the same control-command principles as steel-wheel systems.
In different parts of the world metro systems are also known as the underground, subway or tube.
AUSTRIA         ITALIA        
VIENNA         BRESCIA        
.         CATANIA        
.         GENOVA        
.         MILANO        
.         NAPOLI        
.         ROMA        
.         TORINO