The line connects five suburban towns southwest of the city, serving around one million people.

The towns linked by Line 12 are Alcorcón, Leganés, Getafe, Fuenlabrada and Móstoles.

Despite parts of the line running through uninhabited territory, there are no above-ground sections in an effort to facilitate future urban development.

This decrease was mainly caused by renovation works necessitating the temporary closure of sections of the line.

There are plans to extend Line 3 to provide a further interchange station at El Casar.