The Lisbon Metro connects the city centre with the upper and eastern districts, and also reaches some suburbs that are part of the Lisbon metropolitan area, such as Amadora and Loures. It is the fastest way to get around the city and it provides a good number of interchanging stations with other types of transportation. From the Lisbon Airport station to the city centre it may take roughly 25 mins. As of 2018, the Lisbon Metro comprises four lines, identified by individual colours (blue, yellow, green and red) and 56 stations, with a total length of 44.2 km. Several expansion projects have been proposed, being the most recent the transformation of the Green Line into a circular line and the creation of two more stations (Santos and Estrela).